This project opens with a number of conceptual diagrams in order to address some features of medieval astronomy that are taken for granted throughout the Commedia. Dante does not explain the nature of the ecliptic or the motion of the Sun in his poem; instead, he builds astronomy into the poem with the immediate assumption that his readers will have some understanding of the basics of the Ptolemaic system. I have decided that it would be most effective and most efficient to cover those fundamental concepts prior to treating any sections of the poem. At the same time, however, I have also decided not to anticipate in my diagrams anything that Dante invents before it is presented to us.
Dante is a poet who uses astronomy—not an astronomer who uses poetry. For this reason, it is critical to always bear in mind that astronomy in the Commedia serves as a tool in the poet’s endeavor to craft a compelling narrative. Part of that craft is world-building. In my study of Dantean astronomy, I have found that the astronomical references sprinkled throughout the poem incrementally underwrite a portion of this poetic process of world-building. For example, in Inferno 2, by means of an astronomical periphrasis Virgilio will quickly introduce the concept of the heavenly spheres, which will eventually come to serve as the setting for the entire third cantica. Similarly, in Purgatorio 4, by means of a lengthier and imagined discourse on astronomy Virgilio will generate a precise geographic location for Mount Purgatory, one of Dante’s most striking inventions and the setting of the entire second cantica. While astronomy is by no means the sole tool Dante uses to build out his world, it certainly does some of the heavy lifting.
Traditionally, maps and diagrams of the journey undertaken in the Commedia present an amalgamation of Dante’s world: they include the rings of Hell in the northern hemisphere, Mount Purgatory in the southern hemisphere, and the heavenly spheres encircling the Earth. Modern editions of the Commedia tend to print maps and diagrams of this sort before the text of the poem, and for good reason. Providing such a total image of Dante’s journey is exceedingly useful—I myself have consulted them many times when reading the Commedia in order to track the relative progression of the narrative and visualize the journey as a whole. But the opportunity cost of the decision to condense and display all of Dante’s inventions at the beginning of the Commedia is that it anticipates, and therefore deflates, the spectacle of his craft. In order to preserve and emphasize the effect of astronomy in the poem, my diagrams will not anticipate the poem’s inventions until they are made explicit. For those who are familiar with the traditional maps and diagrams that accompany the Commedia, the most noticeable result of this decision is that my diagrams do not feature Mount Purgatory until Inferno 34. As a substitute for the traditional depiction of Dante’s Earth, I will use a sketch of our planet which more closely resembles the way we see the world today. Once the poem makes it clear that it is breaking away from our world, my diagrams will follow suit.