Astronomical Images : Cosmological spheres and orbs

Johannes Sacrobosco

Astronomical Images

Very little is known about Johannes Sacrobosco except that he was probably British, taught astronomy at Paris University, and died there in the second quarter of the thirteenth century. Sphaera mundi, his major work, was an extraordinarily popular astronomical textbook for several generations. Manuscripts of it circulated through all the main European centres of learning. It was first published in 1472 in Ferrara, and went through dozens of editions up to the mid-seventeenth century. This is from one of the first Italian translations of Sacrobosco's Sphaera, to which Fra Mauro Fiorentino added a short treatise on cosmography, navigation, altimetry and stereometry. Fra Mauro Mattei from Florence or Fiorentino (c. 1493-1556) was a Servite active at the Annunziata Church in Florence. His interests covered several mathematical disciplines, including music (on which a treatise by him survives at the Laurenziana Library). At the beginning of his edition, Fra Mauro included a dedicatory letter to Giovan'Orthega de Carion, from the Annunziata Church, 1537. This Italian translation of Sacrobosco's classic work on the Sphere would have provided a useful resource for those who wanted to improve their knowledge of cosmography but lacked the Latin skills to read the original text, or preferred to read the vernacular version. This figure shows the elemental and celestial spheres. The Earth is divided into three parts, namely Asia, Africa and Europe. Sacrobosco describes the substantial sphere (as opposed to the accidental sphere) in the following way: 'By substance it is divided into the ninth sphere, which is called the 'first moved' or the primum mobile; and the sphere of the fixed stars, which is named the 'firmament'; and the seven spheres of the seven planets, of which some are larger, some smaller, according as they the more approach, or recede from, the firmament. Wherefore, among them the sphere of Saturn is the largest, the sphere of the moon the smallest'.