Medieval European Astronomy (11th-15th Century)

In 1085 Toledo in Spain was taken from the Muslims by the king of Castile and Leon, Alfonso VI (c.69; r.1072-1109), and it soon became the capital of Castile.

A scholarly community rose under the leadership of the archbishop Raymond de Sauvetat (r.1125-52), who knew of the wealth of knowledge possessed by the Muslims and desired for Christendom to gain access to it. Under Raymond’s patronage, translating giants such as Gerard of Cremona (c.1114-87) and John of Seville (fl.1135-53) flourished and schools developed around them. Toledo attracted other first rate scholars from all over Europe including Adelard of Bath (c.1080-c.1150), Robert of Chester (1140s), Rudolf of Bruges 12th century) and Hermann of Carinthia (c.1100-c.1160). 

Gerard of Cremona (c.1114-87) is credited with translating the rules for the use of the Toledan Tables (1175). When these were adapted for latitudes in Western Europe it became possible to predict planetary positions and compare them with subsequent observations. The underlying theories, however, remained a mystery until the Almagest became available.

Alfonso X the Wise (63; r.1252-1284), king of Castile and Leon, had many Arabic works translated into Castilian. He engaged Muslim and Jewish astronomers to prepare the Alfonsine Tables (c.1272) of planetary movements. These soon replaced the Toledan Tables inherited from the Arabs.

A number of medieval thinkers grappled with the question of Earth’s motion. Aristotle taught that the planets performed their motions because their spheres were ensouled. Jean Buridan (1300-1358/61) proposed that the spheres move because of a purely physical ‘impetus’ that was planted in them at their creation and has kept them going ever since. In Paris, Buridan’s pupil, Nicole Oresme (1325-82), argued that all celestial phenomena would appear exactly the same way if Earth were supposed to perform a daily rotation about its axis. The German scholar Nicholas of Cusa (1401-1464) asserted that Earth rotates around the Sun and that Earth moved on its axis, and that the stars were other suns and other worlds revolved around them in the way Earth revolves about the Sun.