Gerbert’s Introduction to the Geocentric Astronomy

Marek Otisk


This paper deals with four astronomical tools made and used by Gerbert of Aurillac, archbishop of Rheims and Ravenna, abbot of Bobbio and in 999–1003 pope (under the name Sylvester II.). Gerbert taught quadrivium mainly in Rheims and from his pupil Richer of Rheims (chronicle Historiarum libri quatuor) and from Gerbert’s letters (addresed to his friend and pupil Constantine of Fleury) we know four of his tools, which offered simple and illustrative introduction to the geocentric system of the world: 1. the globe of the world sphere with an adjustable horizon; 2. the observational hemisphere with five parallel circles of world sphere (two polar circles, two tropics and equator); 3. the planetary sphere with zodiac and orbits of planets on the inside and 4. the armillary sphere with stars and constellations on the outside.


Gerbert of Aurillac; early medieval thinking; astronomy; geocentric system

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TEORIE VĚDY / THEORY OF SCIENCE – journal for interdisciplinary studies of science is published twice a year by the Institute of Philosophy of the Czech Academy of Sciences (Centre for Science, Technology, and Society Studies). ISSN 1210-0250 (Print) ISSN 1804-6347 (Online) MK ČR E 18677 web: /// email: