Gerlandus Compotista

Gerlandus Compotista (* approx. 1030/40; † probably 1102) was an important Lorraine computist, astronomer and mathematician of the 11th century.

Life

Little is known about the life of the computist Gerland. He came from Lorraine and there from the German-French language border. His creative period, in which he probably worked as a teacher, falls in the second half of the 11th century. If we correctly interpret verses in a Computus manuscript from the Cistercian Abbey of Hauterive (Switzerland) , he died in 1102.

Works

Two works by Gerland have survived. The one surviving work is a computus comprising two books . In the first book, he presents the traditional computus, mainly excerpting and summarizing Beda's De temporum ratione and Helperich's Liber de computo . The highlight of the first book is the presentation of a corrected counting of the year, in which seven years are subtracted from the years of the Lord according to Dionysius (Chapters 24-26). The first book ends with computist notes of varying content. In the second book, in which he deals with a “natural computus”, Gerland makes numerous calculations on the course of the moon. In particular, the sidereal and synodic orbital periods are calculated exactly on the basis of the metonic cycle and a theory of eclipses is established . The conclusion is formed by his new moon tables, based on the solar eclipse of September 23, 1093 , in which he gives all new moons in a 76-year cycle to the exact hour.

Gerland's Regulae super abacum are a short, lively written introduction to the use of monastery tobacco . In it, the author pays particular attention to arithmetic with fractions, to illustrate this by distributing 100 marks among eleven merchants as an example. For the first time, the work uses the Ghubar digits and the associated numerals throughout . It quickly gained canonical prestige ( Borst ).

There are still fragments of a description of the Tabula Gerlandi that possibly go back to him. Whether a musical fragment can also be ascribed to him remains questionable.

His two main works were frequently copied and used in the 12th and partly in the 13th century.

literature

• Alfred Lohr (Ed.): The Computus Gerlandi. Edition, translation and explanations. Steiner, Stuttgart 2013, ISBN 978-3-515-10468-5