Medieval Europe

In the Latin West the level of scientific learning had sunk to a low level. None of the Greek works most important for ancient astronomy and cosmology—Aristotle’s On the Heavens and Ptolemy’s Almagest, Handy Tables, and Planetary Hypotheses—were available. The teaching of astronomy was based on a number of low-level Latin accounts. Book II of Pliny the Elder’s Naturalis historia (Natural History, 1st century CE) contained a summary of astronomical matters. In the 4th century Martianus Capella wrote an allegorical poem, De nuptiis Philologiae et Mercurii (The Marriage of Philology and Mercury). In the two introductory books, Philology, personified as a maiden, is wed to Mercury, patron god of learning. In the following seven books, each of the Liberal Arts, including Astronomy, personified as a handmaid to Philology, steps forward to give an account of her art. Martianus’s Marriage was widely admired in the early Middle Ages as a compendium of all useful learning.

In the 12th and 13th centuries, two developments were key to the revival of astronomy in the Latin West. The translation movement rapidly made available key works of Greek astronomy that had long been out of reach. One of the most important translators was Gerard of Cremona. As his students later wrote of him, he had learned everything that was known to the Latins, but for love of the Almagest, which he had heard of but which was unavailable in Latin, he went to Spain and learned Arabic well enough to translate it. Thus, one could maintain that a major reason for the revival of learning in the West was one man’s desire to be able to read Ptolemy. Gerard translated from Arabic versions not only Ptolemy’s Almagest but also Aristotle’s On the Heavens, Euclid’s Elements, and about two dozen other works of astronomy and geometry. In a single generation most of the key works of ancient astronomy became available.

The second important development was the foundation of the European universities, starting with those of Bologna, Paris, and Oxford. Because astronomy figured among the liberal arts, it had a place in the university core curriculum. Of course, the astronomy of the liberal arts curriculum was at a rudimentary level. The students might be taken though an introduction to the celestial sphere—for example, the De sphaera mundi (“On the Sphere of the World,” c. 1230) by Johannes de Sacrobosco, which might be followed by the anonymous Theorica planetarum (“Theories of the Planets”), a superficial introduction to eccentrics and epicycles. Nevertheless, in every university town there had to be someone charged with teaching astronomy.

In the 1270s a new set of astronomical tables was compiled in Spain under the patronage of the Christian king Alfonso X of Léon and Castile. These were based on standard Ptolemaic astronomy, with some differences in the treatment of precession (now considered to occur at a variable speed). By 1320 the Alfonsine Tables had reached Paris, where they were reworked by several Parisian astronomers. From there they spread all over Latin Europe, and for more than two centuries they were the standard.