Sacrobosco's Tracts „The Sphere“

Accumulation of Knowledge and the Tradition of Sacrobosco's Tracts „The Sphere“

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Distribution of the climate zones on the terrestrial sphere. From Sacrobosco, Johannes de: Libellvs de Sphaera, 1568.

During the 13th century, a new tract on elementary spherical astronomy and cosmology was compiled: The Sphere of Johannes de Sacrobosco. The tract reflects the new requirements of late medieval society that were related to the emergence of a greater dynamic among individuals such as merchants, academicians, officers and especially students, who increasingly began to travel. The tract contains the knowledge that travelers needed to be able to orient themselves and use instruments such as the quadrant and the astrolabe—instruments required for measuring time and locating positions. The tract also immediately underwent a process of transformation through commentaries so that The Sphere soon became a formal scientific tradition that lasted until the 17th century, well beyond the diffusion of the printed book and, above all, the Copernican Revolution. The innumerable commentaries on The Sphere produced between the 13th and 17th centuries enriched the original tract with an increasing number of subjects that reflected the economic, scientific and political situation of the regions in which the tracts were produced. The Sphere immediately also became a mandatory course at the faculties of liberal arts at most of the European Universities, whose network rapidly expanded.

In 1564, for instance, a Florentine scholar, Francesco Giuntini, published a tract entitled La sfera del mondo in Lyon. In this work, the four originally short chapters turned into four voluminous books. The most relevant addition of Francesco Giuntini to the original tract is a subject that connects practical optics with geographical issues. Giuntini explains how to use observational instruments like the astrolabe and especially the more manageable quadrant. In the early modern period, such instruments were needed whenever a person needed to establish their own location, for instance during a trip and especially, the time according to that location. In 1604, Francesco Pifferi, a lecturer of mathematics at the Studio in Siena, published a beautifully commented edition of The Sphere in Siena: Sfera di Giovanni di Sacrobosco. Among the many subjects broached, Pifferi added a systematic description of the winds on the basis of the data collected during worldwide travels of exploration, a long chapter on the art of navigation and a complete section dedicated to the measuring devices of the period and their functioning.

The paper intends to show how the tradition of knowledge formalized in the form of the tracts on The Sphere finds its deepest historical meaning beyond the limits of the discipline 'Astronomy' and can be rather seen as a the result of the accumulation of practical knowledge needed in the context of travels. As such process of accumulation was powered by the creative junction between astronomy and the re-emerging metrical geography of the early modern period, while focusing especially on the 16th century, the research aims to understand the mechanisms and conditions of accumulation processes such as the continuously re-iterated invariant structure of the text which assured a stable knowledge system.

The paper will address the attention to mainly 16th century tracts on The Sphere produced in different locations in Europe. Moreover, It will connect these sources to evidence extrapolated from travel reports like those collected by Giovan Baptista Ramusio, the diaries of Marino Sanuto and the writings of Richard Hakluyt.