This is a virtual space dedicated to my current research project on the Sphere of Johannes de Sacrobosco.


I am writing a book about one of the most successful scientific textbooks of all time, the De sphaera (On the sphere) of Johannes de Sacrobosco (ca. 1200 – ca. 1250). Sacrobosco, an Englishman who taught in the Arts Faculty of the University of Paris in the early thirteenth century, composed the Sphere sometime around 1230 as an introductory astronomy textbook for university students. The book rapidly became the most popular and widely used astronomy textbook of the medieval and early modern period, serving as the basis for introductory astronomy lectures at universities throughout Europe from the mid-thirteenth to the end of the seventeenth century. As astronomy was part of the basic arts curriculum which all students had to complete before advancing to any of the higher faculties, a very high percentage of university-educated men would have been exposed to this text. Moreover, it is clear that the Sphere was read outside of the university context as well. In addition, the text was translated into different vernacular languages. Thus a broad swath of educated Europeans, both men and women, were interested in and had access to Sacrobosco’s Sphere. There are at least one hundred extant manuscripts of the Sphere, and over two hundred different editions printed between 1472 and 1673. The majority of these were in Latin, but there were also versions in German, English, French, Italian, Spanish, Portuguese and even Chinese.

Despite its popularity and longevity, there is no book-length study of Sacrobosco’s Sphere and its place in European intellectual life. Historians of science have largely ignored the Sphere because it is a textbook that was intended to give a very basic, non-technical introduction to cosmology. (Exceptions include the work of Lynn Thorndike, Owen Gingerich, and Olaf Pedersen.) Further, its very longevity has caused it to fall into disrepute. That a text by a thirteenth-century author was still in use barely more than a decade before Isaac Newton published his Principia Mathematica (1687), the foundational text of modern physics, seems to embody the conservatism of medieval and early modern pedagogy, a conservatism that the heroes of the so-called Scientific Revolution, Copernicus, Galileo, Kepler and Newton all rebelled against. Yet it is my contention that the Sphere played a key and hitherto undocumented role in the dissemination of new knowledge about the heavens and the earth. Far from remaining static for four centuries, the Sphere – in both manuscript and print – was generally accompanied by additions, corrections and commentary. Some sixteenth-century editions, for example, incorporated discussion of Christopher Columbus’s voyages to America and noted that this necessitated modification of Sacrobosco’s assertion that the equatorial region was too hot to support life. And some seventeenth-century Spheres included reports of Galileo’s telescopic observations. The Sphere was an important vehicle for dissemination of new discoveries and for discussion of how these new discoveries could or could not be reconciled with traditional theoretical frameworks.

My goal with this book is to tell the story of the rise of modern science in the sixteenth and seventeenth centuries from a new perspective. Rather than focusing exclusively on the great discoveries and brilliant theories that transformed understandings of the natural world, I devote equal attention to the more messy and mundane efforts of a wide variety of authors and readers to come to terms with new knowledge and ideas. In some cases this meant integrating new findings into older systems of understanding the world, and in other cases this meant jettisoning those older systems in favor of new ones. I acknowledge, as do all historians of the Scientific Revolution, the contributions of famous innovators from Copernicus to Newton, but I give equal weight to the more ordinary intellects – university professors and their students, printers and hack writers, rulers and their courtiers, artisans and navigators, women as well as men – who helped to forge a new view of the cosmos and the place of human beings in it.

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