Scientist of the Day - Johannes de Sacrobosco

Planetary model for Mercury, hand-colored woodcut, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

Johannes de Sacrobosco was a 13th-century cleric and astronomer who wrote a basic textbook on astronomy called The Sphere. It was the single most popular astronomical textbook until 1600, and one of the first such books to be printed. We have an edition printed in Venice in 1478 by Franz Renner, which we discussed in a post in 2022, where we provided some more detail about Sacrobosco, and promised to discuss some of our other early editions of the Sphere on a future occasion. That occasion has arrived.

First paragraph and initial letter, printed in red and black, listing Sacrobosco, Regiomontanus, and Peurbach among the authors included, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

Armillary sphere, woodcut frontispiece, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

Our second printed edition of Sacrobosco was published in Venice in 1482. The printer was a noted emigre from Augsburg, Erhard Ratdolt, the most prolific publisher of scientific books in all of Europe in the last two decades of the 15th century. It was Ratdolt who published the first edition of Euclid’s Elements in 1482 that we featured just last week in a post on Euclid.

Geocentric cosmos, woodcut, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

Planetary model for the Sun, hand-colored woodcut, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

Ratdolt's Sphere is even more beautiful than Renner's. It has a frontispiece, depicting an armillary sphere (third image), an appropriate addition to a book called The Sphere; a depiction of the geocentric cosmos (fourth image); and it has even more hand-colored woodcuts than Renner’s.   Renner's 1478 edition had included a medieval treatise, the Theory of the Planets, to explain the basic epicycle-deferent models of Ptolemaic astronomy.  Ratdolt substituted a recent Renaissance publication, the New Theory of the Planets, by the Viennese astronomer, Georg Peurbach.  The text of Peurbach’s New Theory begins immediately after the Sphere concludes, without so much as a page break, so it is easy to miss the fact that you have transitioned from medieval astronomy to Renaissance astronomy.  We show here the woodcuts that illustrate the model for the motion of the Sun (fifth image), and that of Mercury (first image). These were printed in black and then colored by hand, which you can detect yourself with a magnifying glass (or view our seventh image), since the colorist strayed occasionally from the printed lines.

Lunar eclipse diagram, hand-colored woodcut, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

Detail of sixth image, showing the hand-coloring, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

You probably noticed that we did not show you a title page for this book, because the title page had not yet been invented (Ratdolt himself did invent it, but not here).  For information on the publisher and the place and date of publication, we have to turn to the colophon on the very last page, where we learn that Erhard Ratdolt published it in Venice on July 2, 1482 (eighth and ninth images). 

Last page, with diagram of the motion of the eighth sphere, and the colophon, as well as user annotations, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

Colophon, detail of eighth image, showing Venice, Erhard Ratdolt, and 1482 as the place, publisher, and date of publication, Sphaera mundi, by Johannes de Sacobosco, 1482 (Linda Hall Library)

Chronologically, our next edition of Sacrobosco's Sphere was published in 1490, an edition in which the woodcuts were printed in color, instead of having the coloring added by hand. We will not wait another four years to talk about it, but should have our third Sacrobosco post ready in a week or two.

William B. Ashworth, Jr., Consultant for the History of Science, Linda Hall Library and Associate Professor emeritus, Department of History, University of Missouri-Kansas City. Comments or corrections are welcome; please direct to ashworthw@umkc.edu.