He had learned about Ptolemaic cosmology from the Moors. Then the Sun and the planets revolve around the Earth and follow a number of nested circular motions.
On the basis of this view of the world, he estimated the movement of the planets as accurately as possible. The most accurate planetary tables up to that point were completed in 1270, after nearly two decades of work.
The calculations were directed by scholars Jehuda ben Mose and Isaac ben Sid, about whose lives little is known. The two wrote one of the most important works in the history of astronomy, although it was named after the project’s patron.
The “Alphonse Tables” attracted attention across Europe—and shaped astronomy for two centuries. But the tables were based on a false assumption: Earth is not at the center of the Solar System.
This defect became more apparent over time. Around the year 1500, the planets in the sky were four full moon diameters away from the positions given in the Alphonsine tables.
This made a certain Nicolaus Copernicus think of a new worldview – after all he very wisely moved the Earth to the edge and the Sun to the center of the planetary system.
The Life of Alfonso X.
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