Medieval Astronomy

With the fall of Rome, much of the astronomy of the classical age was lost to Europeans. Medieval beliefs about the universe were distilled partly from Plato (via a commentary on Cicero’s Dream of Scipio by a fifth-century Latin scholar named Macrobius), but mostly from the philosophical works of Aristotle. In the Aristotelean cosmos, the Earth is an unmoving sphere which sits at the center of the universe. The known planets and a sphere of fixed stars move uniformly in a circular motion around the Earth, with the Moon closest to the center, followed by Mercury, Venus, the Sun, Mars, Jupiter, and Saturn.

Astronomy was revived in Europe during the eleventh century with the arrival of the astrolabe, a device for measuring the position of heavenly bodies which was introduced to Europe from the Islamic world. Planetary observations were useful for astrological predictions and for medical practice, since the planets and the zodiac were thought to correspond to the organs of the human body. Over the next century, the writings of ancient Greek astronomers like Ptolemy were rediscovered by the West, further enriching Europe’s knowledge of the universe. Astronomy was one of the seven liberal arts taught to students in the Arts curriculum at medieval universities; textbooks transmitted basic theories about the cosmos and the mathematics needed to calculate the movement of heavenly bodies in a simplified version of Ptolemy. Some of these texts were still being used by students well into the sixteenth and seventeenth centuries.


Selected resources at L. Tom Perry Special Collections

Aristotle. De Caelo (Of the heavens). Augsburg: Sigmund Grimm and Marx Wirsung, 1519.

One source for Aristotle’s teachings about the celestial spheres. This edition is bound with other printed versions of Aristotle’s works on physics and meteorology.

Call number: Vault Collection Quarto 888.58 Ec51 1518


Ptolemy. Almagest. Venice: Peter Liechtenstein, 1515.

Ptolemy’s Almagest (from the text’s Arabic name, meaning “The Great Book”), which dates from the mid-second century AD, was probably the most important of these rediscovered texts. The Almagest describes Aristotle’s Earth-centered universe and the movement of the Sun, Moon, known planets, and stars. Ptolemy also created a catalog of stars and planetary positions based on his own observations and the work of the Greek astronomer Hipparchus (c. 194-120 BC). But the geometric models Ptolemy used to fit these observations to Aristotle’s circular spheres were highly complex, moving the Earth slightly off-center in the middle of the revolving spheres and introducing extra circular movements to explain the apparent backward (retrograde) motion of planets in the sky. Ptolemy required 55 spheres to carry all of the known celestial objects.

This is the first printed edition of the Almagest, in a Latin translation by Gerard of Cremona (the book was first printed in the original Greek in 1538).

Call number: Vault Collection 091 B47L


Johannes de Sacrobosco. De Sphaera (The Sphere). Bound with Georg von Peurbach. Theoricae novae planetarum (New theory of the planets). Venice: Erhart Ratdolt, 1485.

Two of the major astronomy textbooks in the early Renaissance. Sacrobosco’s De sphaera dates from the mid-thirteenth century, while Peurbach’s work was first published in 1474. This edition of these texts is unique in the history of printing because it is the first book with color illustrations printed using multiple wooden blocks

Call number: Vault Collection 093 R186 1485 no.3


Tabulae astronomice divi Alfonsi Regis Romanorum et Castelle (Alfonsine Tables). Venice: Peter Liechtenstein, 1518.

These planetary tables, which calculate the position of the planets in the sky as seen at various latitudes on Earth, were compiled in Toledo under the patronage of the Spanish king Alfonso X in the latter half of the 13th century. They were widely used until new tables were issued by astronomers like Erasmus Reinhold and Johannes Kepler nearly four centuries later.

Call number: Vault Collection Quarto 520.9 Al75 1518


Selected online resources

An astronomical manuscript (France, 11th and 12th centuries) at the National Library of Wales
This illustrated manuscript contains a Latin translation of a Greek text by Aratus of Soli on the constellations, as well as Cicero’s The Dream of Scipio with the commentary by Macrobius.

A manuscript of Sacrobosco's Algorismus and Tractatus de Sphaera (Italy, mid-13th century), Schoenberg Center for Electronic Text and Image, University of Pennsylvania
Another illustrated manuscript, with marginal notations.