Embedding New Theory in Brass: Alfonsine Trepidation Spheres

This abstract has open access
Abstract Summary
The slow changing position of the fixed stars with respect to the vernal point, directly observable through the stars’ changing ortive amplitude, were accounted for by diverging models during the Middle Ages. Ptolemy assumed a linear increase of stellar longitude over time. A text on the movement of the Eighth Sphere (the sphere of the fixed stars), sometimes attributed to Thābit ibn Qurra, circulated in the West and described a back-and-forth movement. In the Latin world this movement of “access and recess” was termed trepidation. The Toledan tables (11th c.) included this same movement of trepidation. In the Castilian Alfonsine tables (ca. 1270) trepidation of the Eighth Sphere is also considered. In Parisian Alfonsine astronomy those secular changes are described by combining a linear change (one revolution in 49000 years) with a trepidation movement. Very few spatial, material representations of these aspects of astronomical theories are known: today only about a dozen surviving armillary spheres are modelling the phenomenon of trepidation. Some such trepidation spheres from the 16th century are signed by the famous G. Arsenius. A systematic description and comparison of these spheres is still lacking. An outline of such a comparative study will here be proposed. It will have to tackle the relationship between competing theories, astronomical tables and canons on the one hand and visual representations, including diagrams and material models, like armillary spheres, on the other.
Abstract ID :
HSS455
Submission Type
Abstract Topics
Chronological Classification :
Medieval

Abstracts With Same Type

Abstract ID
Abstract Title
Abstract Topic
Submission Type
Primary Author
HSS575
Aspects of Scientific Practice/Organization
Organized Session
Prof. Anna Graber
HSS355
Technology
Organized Session
Francesco Cassata
HSS587
Medicine and Health
Organized Session
Chantal Marazia
HSS872
Thematic Approaches to the Study of Science
Organized Session
Dr. Alison Kraft
HSS5847
Biology
Organized Session
Dr. Dominik Huenniger
HSS512
Aspects of Scientific Practice/Organization
Organized Session
Alrun Schmidtke
104 visits