De sphaera mundi
De sphaera mundi (
Latin title meaning On the Sphere of the World,
sometimes rendered The Sphere of the Cosmos; the
Latin title is also
given as Tractatus de sphaera, Textus de sphaera, or simply De
sphaera) is a medieval introduction to the basic elements of astronomy
Johannes de Sacrobosco
Johannes de Sacrobosco (John of Holywood) c. 1230. Based
heavily on Ptolemy's Almagest, and drawing additional ideas from
Islamic astronomy, it was one of the most influential works of
pre-Copernican astronomy in Europe.
2.1 The universe as a machine
2.2 Spherical Earth
5 External links
De sphaera mundi
De sphaera mundi was the most successful of several
competing thirteenth-century textbooks on this topic. It was used in
universities for hundreds of years and the manuscript copied many
times before the invention of the printing press; hundreds of
manuscript copies have survived. The first printed edition appeared in
1472 in Ferrara, and at least 84 editions were printed in the next two
hundred years. The work was frequently supplemented with commentaries
on the original text. The number of copies and commentaries reflects
its importance as a university text.
The 'sphere of the world' is not the earth but the heavens, and
Sacrobosco quotes Theodosius saying it is a solid body. It is divided
into nine parts: the "first moved" (primum mobile), the sphere of the
fixed stars (the firmament), and the seven planets, Saturn, Jupiter,
Mars, the sun, Venus, Mercury and the moon. There is a 'right' sphere
and an oblique sphere: the right sphere is only observed by those at
the equator (if there are such people), everyone else sees the oblique
sphere. There are two movements: one of the heavens from east to west
on its axis through the Arctic and Antarctic poles, the other of the
inferior spheres at 23° in the opposite direction on their own axes.
The world, or universe, is divided into two parts: the elementary and
the ethereal. The elementary consists of four parts: the earth, about
which is water, then air, then fire, reaching up to the moon. Above
this is the ethereal which is immutable and called the 'fifth essence'
by the philosophers. All are mobile except heavy earth which is the
center of the world.
The universe as a machine
Sacrobosco spoke of the universe as the machina mundi, the machine of
the world, suggesting that the reported eclipse of the
Sun at the
crucifixion of Jesus was a disturbance of the order of that machine.
This concept is similar to the clockwork universe analogy that became
very popular centuries later, during the Enlightenment.
Picture from a 1550 edition of De sphaera.
Though principally about the universe, De sphaera contains a clear
description of the
Earth as a sphere which agrees with widespread
opinion in Europe during the higher Middle Ages, in contrast to
statements of some 19th- and 20th-century historians that medieval
scholars thought the
Earth was flat. As proof, he uses the fact
that stars rise and set sooner for those in the east, and lunar
eclipses happen earlier; that stars near the
North Pole are visible to
those further north and those in the south can see different ones;
that at sea one can see further by climbing up the mast; and that
water seeks its natural shape which is round, as a drop.
^ Olaf Pedersen, "In Quest of Sacrobosco", Journal for the History of
Astronomy, 16 (1985): 175-221. Pedersen identifies 35 printings in
Venice, another 35 in Paris, and more in 14 other cities throughout
^ John of Sacrobosco, On the Sphere, quoted in Edward Grant, A Source
Medieval Science, (Cambridge: Harvard Univ. Pr., 1974), p.
^ Jeffrey Burton Russell, Inventing the Flat
Earth (New York: Praeger,
1991): 19, 26–27. ISBN 0-275-93956-1.
Pedersen, Olaf. "The Corpus Astronomicum and the Traditions of
Latin Astronomy: A Tentative Interpretation. pp. 59–76
Owen Gingerich and Jerzy Dobrzycki, eds., Colloquia Copernicana
III. Wrocław: Ossolineum, 1975.
Thorndike, Lynn. The Sphere of Sacrobosco and its Commentators.
Chicago: Univ. of Chicago Press, 1949.
Media related to
De sphaera mundi
De sphaera mundi at Wikimedia Commons
Summary of the contents of each chapter
Sacrobosco's De Sphaera – complete treatise in English translation
Book, The Sphere of Sacrobosco and its Commentators, by Lynn
Thorndike, year 1949. Text in Latin, English translation, and
Treasures of the RAS: The Sphere by John of Hollywood on YouTube
Selected images from Sphaera mundi From The College of Physicians of