Nicolaus Copernicus "Almagest" circa 150 CE; the Earth was the stationary center of the universe. Stars were embedded in a large outer sphere which rotated rapidly, approximately daily, while each of the planets, the Sun, and the Moon were embedded in their own, smaller spheres. Ptolemy's system employed devices, including epicycles, deferents and equants, to account for observations that the paths of these bodies differed from simple, circular orbits centered on the Earth. Copernicus' major work on his heliocentric theory was "Dē revolutionibus orbium coelestium" ("On the Revolutions of the Celestial Spheres"), published in the year of his death, 1543. He had
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