machine. This concept is similar to the clockwork universe analogy that became very popular centuries later, during the Enlightenment. Spherical Earth Though principally about the universe, De sphaera 1230 A.D. 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 evidence for the Earth being a sphere, in Chapter One he cites the observation that stars rise and set sooner for those in the east ("Orientals"), 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. See also Armillary sphere Orrery References Sources External links 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 commentary. Selected images from Sphaera mundi From The College of Physicians of Philadelphia Digital Library 1230s books Astronomy books Astrological texts 13th-century Latin books Treatises pt:Johannes de Sacrobosco