Article ID: CBB755611640

THE MERCURY MODELS OF IBN AL-ŠĀṬIR AND COPERNICUS (2019)

unapi

Copernicus' complex Mercury model in De revolutionibus is virtually identical, geometrically, to Ibn al-Šāṭir's (ca. 1305 – ca. 1375). However, the model in his earlier Commentariolus is different and in many ways unworkable. This has led some to claim that the younger Copernicus did not understand his predecessor's model; others have maintained that Copernicus was working totally independently of Ibn al-Šāṭir. We argue that Copernicus did have Ibn al-Šāṭir's models but needed to modify them to conform to a “quasi-homocentricity” in the Commentariolus. This modification, and the move from a geocentric to heliocentric cosmology, was facilitated by the “heliocentric bias” of Ibn al-Šāṭir's models, in which the Earth was the actual center of mean motion, in contrast to Ptolemy and most Islamicate astronomers. We show that: 1) Ibn al-Šāṭir sought to reproduce Ptolemy's critical elongation at the trines(±120°), but changed the Ptolemaic values at 0, ±90, and 180°; 2) in the Commentariolus, Copernicus does not try to produce viable elongations for Mercury; and 3) by the time of writing De revolutionibus, Copernicus is in full control of the Mercury model and is able to faithfully reproduce Ptolemy's elongations at all critical points. We also argue that claims regarding “natural” solutions undermining transmission are belied by historical evidence., Le modèle complexe de Mercure dans le De revolutionibus de Copernic est virtuellement identique, géométriquement, à celui d'Ibn al-Šāṭir (ca. 1305 – ca. 1375). Cependant, le modèle, antérieur, du Commentariolus est différent et il fonctionne mal. Certains en ont déduit que le jeune Copernic n'avait pas compris le modèle de son pré- décesseur; d'autres ont affirmé que l'œuvre de Copernic était totallement indépendante d'Ibn al-Šāṭir. Nous soutenons que Copernic avait les modèles d'Ibn al-Šāṭir mais qu'il a dû les modifier pour les rendre “quasi-homocentriques” dans le Commentariolus. Cette modification et le passage d'une cosmologie géocentrique à une cosmologie héliocentrique étaient rendus aisés par le “biais héliocentrique” des modèles d'Ibn al-Šāṭir, pour qui la Terre était le centre effectif du mouvement moyen, contrairement à Ptolémée et à la plupart des astronomes islamiques. Nous montrons que : 1) Ibn al-Šāṭir a cherché à reproduire les élongations critiques à ±120° de l'apogée, mais il a changé les valeurs ptoléméennes à 0, ±90 et 180° ; 2) dans le Commentariolus, Copernic n'essaie pas de reproduire des élongations viables pour Mercure;et 3) au moment de la rédaction du De revolutionibus, Copernic contrôle pleinement le modèle de Mercure et il est capable de reproduire les élongations de Ptolémée aux points critiques. Nous soutenons aussi que les arguments concernant des solutions “naturelles” qui excluent la transmission sont niés par l’évidence historique.

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Authors & Contributors
Segonds, Alain-Philippe
Lerner, Michel-Pierre
Graney, Christopher M.
Goddu, André
De Pace, Anna
Timberlake, Todd
Journals
Journal for the History of Astronomy
Early Science and Medicine: A Journal for the Study of Science, Technology and Medicine in the Pre-modern Period
Osmanli Bilimi Arastirmalari: Studies in Ottoman Science
Journal of Astronomical History and Heritage
History of Science
Bruniana & Campanelliana: Ricerche Filosofiche e Materiali Storico-testuali
Publishers
Les Belles Lettres
Edizioni Ca’ Foscari Venice University Press
University of Notre Dame Press
Springer
Oxford University Press
Olschki
Concepts
Astronomy
Heliocentrism
Cosmology
Copernicanism
Geocentrism
Celestial mechanics
People
Copernicus, Nicolaus
Galilei, Galileo
Kepler, Johannes
Brahe, Tycho
Regiomontanus (Jahannes Mueller)
Aristarchus, of Samos
Time Periods
16th century
Renaissance
17th century
15th century
Ancient
Early modern
Places
Italy
Lisbon (Portugal)
Portugal
Greece
Europe
Institutions
Jesuits (Society of Jesus)
Comments

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