_full_journalsubtitle: A Journal for the Study of Science, Technology and Medicine in the Pre-modern Period _full_abbrevjournaltitle: ESM _full_ppubnumber: ISSN 1383-7427 (print version) _full_epubnumber: ISSN 1573-3823 (online version) _full_issue: 2 _full_issuetitle: 0 _full_alt_author_running_head (neem stramien J2 voor dit article en vul alleen 0 in hierna): 0 _full_alt_articletitle_running_head (rechter kopregel - mag alles zijn): A Medieval European Value for the Circumference of the Earth _full_is_advance_article: 0 _full_article_language: en indien anders: engelse articletitle: 0 A Medieval EuropeanEarly ValueScience For and The Medicine Circumference 25 (2020) 135-151 Of The Earth 135 www.brill.com/esm A Medieval European Value for the Circumference of the Earth C. Philipp E. Nothaft All Souls College, Oxford, UK
[email protected] Abstract Geographic and astronomical texts from late-medieval Central Europe frequently give 16 German miles, or miliaria teutonica, as the length of a degree of terrestrial latitude. The earliest identifiable author to endorse this equivalence is the Swabian astronomer Heinrich Selder, who wrote about the length of a degree and the circumference of the Earth on several occasions during the 1360s and 1370s. Of particular interest is his claim that he and certain unnamed experimentatores established their preferred value empir- ically. Based on an analysis of relevant statements in Selder’s extant works and other late-medieval sources, it is argued that this claim is plausible and that the convention 1° = 16 German miles was indeed the result of an independent measurement. Keywords medieval geodesy – medieval astronomy – medieval metrology – circumference of the Earth – Heinrich Selder Regular readers of geographic and cartographic literature printed before 1900 will have come across the concept of the German geographic mile, which was defined as covering one fifteenth of a degree of latitude, making it equi- valent to 4 nautical miles.