Nikephorus Gregoras and Astrolabes
My interest in Byzantine science began with a text, Nikephorus Gregoras’s “περὶ κατασκευῆς καὶ γενέσεως ἀστρολάβου” (“On the Mathematical Origin and Construction of the Astrolabe”). Gregoras was renowned for his skill in both mathematics and the sciences of the stars. He was favored by emperors and helped reestablish the sciences in 14th-century Constantinople. Yet, at first glance the content and form of his text on the astrolabe seems relatively simple, especially compared to the texts circulating in Arabic and Latin. He must have known of these other traditions.
Why then did he write this text?
Who was his intended audience?
How did a text on the astrolabe advance his goals?
Or why did he think a text on the astrolabe would advance his goals?
Gregoras offers a glimpse of the cultural and scientific values of 14th-century Constantinople and the imperial court. What began (and continues) as a study of a text has become an examination of the scientific culture in the imperial capital.
In a fragment attributed to John Kamateros on the astrolabe are a handful of interesting diagrams illustrating the various parts of an astrolabe. Here is the diagram showing the rete. There is also diagram illustrating the plate, and two showing different aspects of the back of the instrument. Read more
Today’s image comes once again from the many diagrams in BL Royal MS 16 C XII. This particular drawing illustrates how the earth’s shadow is cast by the sun. I appreciate the detail the scribe added to the sun, giving it a face complete with attitude. Read more
The standard geocentric model assumed that the planets were arranged out from the center, the earth, according to the period of revolution. On this assumption, the shorter the period, the closer the planet was to the stationary, central Earth. Claudius Ptolemy ensconced the order in his Syntaxis (commonly know as… Read more