And yet at the same time, cosmology had reverted to a naïve and primitive form of geocentrism – with concentric crystal spheres determining the order of the planets and the accompanying hierarchy of angels. The highly ingenious systems of Aristotle’s fifty-five spheres, of Ptolemy’s forty epicycles were forgotten, and the complex machinery was reduced to ten revolving spheres – a kind of poor man’s Aristotle which had nothing whatever in common with any of the observed motions in the sky. The Alexandrian astronomers had at least tried to save the phenomena; the medieval philosophers
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