De revolutionibus orbium coelestium Earth's axis rigidly to a Sun-centered sphere. The unfortunate consequence was that the terrestrial rotation axis then maintained the same inclination with respect to the Sun as the sphere turned, eliminating the seasons." To explain the seasons, he had to propose a third motion, "an annual contrary conical sweep of the terrestrial axis". It was not until the Great Comet of 1577, which moved as if there were no spheres to crash through, that the idea was challenged. In 1609, Kepler fixed Copernicus' theory by stating that the planets orbit the sun not in circles, but ellipses. Only after Kepler's
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