The European Renaissance
We now return to Europe and look at Copernicus (A.D. 1473–1543). His treatise De revolutionibus orbium coelestium [On the revolutions of the heavenly spheres], published in the year of his death, is as substantial as the Almagest, but I will not describe it in such detail. What everyone “knows” about Copernicus is that he made the sun stand still: he considered the sun to be fixed at the center of the universe, the planets to be circling round it, and the earth to move just like any other planet. But this is misleading, if not actually false: Copernicus did not place the sun at the center but near the center of the various orbits, and the earth does not move quite like the other planets (it does not have an epicycle (see page 208)).
KeywordsCircle Center Intermediate Orbit Sidereal Period Assumed Direction Heavenly Sphere
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