Petrus de Dacia (astronomer)

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Petrus de Dacia , Petrus Dacia , Petrus Dacus or Petrus Danus, Latinized for Peter from Denmark, also known as Peter Philomena or Peter Nachtigall, was a Danish clergyman, astronomer and mathematician of the 13th century.

Life

His year and place of birth is unknown. He was originally canon of Roskilde Cathedral . It first appears in a letter from the German Dominican provincial Hermann von Minden (from 1286 to 1290), who thanks him for the donation of some astronomical instruments and advises him to leave Italy and visit Germany. From 1291 to 1292 he is a professor at the University of Bologna, where he taught mathematics and astronomy. In 1292 he is in Paris and is very active as an author there in 1293. After that his traces are lost until 1303, when he can be traced back to Roskilde based on a letter from Pope Boniface VIII (4th July 1303). Since he does not appear in the necrologists of Roskilde Cathedral, he probably died outside of it.

He should not be confused with Petrus von Dacien , a Swedish Dominican of the same name. H. Schück pointed this out as early as 1895, but it was still confused with this in literature. He is also not to be confused with another Petrus de Dacia , who was rector of the University of Paris in 1326/1327.

plant

Over 200 manuscripts of mathematical and astronomical content have been preserved by Petrus Dacus (Olaf Pedersen), some with uncertain attribution. Below is a commentary on the arithmetic textbook by Sacrobosco , which also contains original contributions by Petrus Dacus, for example on the extraction of cube roots. Another work is an astronomical calendar for the years 1292 to 1369 (76 years), which he wrote in Paris as a replacement for the outdated calendar by Robert Grosseteste (with improvements over Grosseteste for the phases of the moon). In the appendix he gives instructions for adapting the calendar for the years 1369 and 1442. His calendar remained in use for over 150 years. The peculiarity of the calendar is that it records the maximum level of the sun and the length of the day for each day, which, according to Alfred Otto, was also the procedure of an unknown astronomer in the partially preserved calendar Liber daticus of 1274 in Roskilde Cathedral, which probably served as a model.

According to the number of surviving manuscripts (68), his most popular work is his moon tables (Tabula lune).

Another important contribution are his manuscripts on astronomical instruments. Among them the Tractatus de semissis (Paris, 1293, received in 10 manuscripts), which comes from a Peter of St. Omer (Petrus de St. Audomaro) and was written in Paris in 1293. According to Olaf Pedersen, this is very likely identical with Petrus Dacus. The treatise describes an equatorium for determining the lengths of the planets in the zodiac, which has been greatly improved by the author compared to the instrument from Campanus of Novara (around 1260) . A corresponding instrument has not survived, but was reconstructed by Olaf Pedersen in 1967.

In his Tractatus novi quadrantis (Paris 1293) he describes a new quadrant by Jacob ben Mahir ibn Tibbon (Profatius Judaeus), which he developed from an astrolabe . The text is a detailed explanation of the text likely translated from Hebrew.

In a Tractatus eclipsorii he describes an equatorium for the determination of eclipses . As in other manuscripts, the information relates to the geographic position of Paris.

literature

  • Olaf Pedersen : Peter Philomena of Dacia, also known as Petrus Dacus, Petrus Danus, Peter Nightingale , in Dictionary of Scientific Biography
  • Ernst Zinner : Petrus de Dacia, a medieval Danish astronomer , Archeion, 18, 1936, pp. 318–329 (translation from Nordisk astronomisk tidskrift, 13, 1932, 136)
  • G. Rasch: Petrus de Dacia in V. Meisen Prominent Danish Scientists through the Ages , Copenhagen University Library, 450th birthday. Levin and Munksgaard, Copenhagen 1932, pp. 12-15
  • Olaf Pedersen: The life and work of Peter Nightingale , Vistas in Astronomy, Volume 9, 1967, pp. 3–10
  • Olaf Pedersen: Petrus Philomena de Dacia: a problem of identity. With a survey of the Manuscripts , University of Copenhagen 1976 (Cahiers de l´Institut du Moyen-Age grec et latin, CIMAGL, Volume 19)

Newer editions of works:

  • Fritz Saaby Pedersen et al. a. (Editor): Corpus Philosophorum Danicorum Medii Aevi , Volume X, Copenhagen 1983, 1984:
    • Volume X, 1: Petri Philomenae de Dacia Opera quadrivialia, 1983
    • Volume X, 2: Petri de S. Audomaro Opera quadrivialia, 1984
  • Fritz S. Pedersen (editor): Petrus De Dacia: Tractatus instrumenti eclipsium , University of Copenhagen 1978 (Cahiers de l´Institut du Moyen-Age grec et latin, CIMAGL, 25, 1978, pp. 23–49)
  • Fritz S. Pedersen (editor): A mediaeval commentary on time-reckoning: computus metricus manualis cum commento Petri de Dacia , University of Odense (Institut for Klassiske Studier, Skrifter) 1979

Individual evidence

  1. ↑ Schück Illustrierte Swedish Literary History , Stockholm, Volume 1, 1895, p. 343 (Swedish), also George Sarton Introduction to the history of Science , Volume 2, 1931, pp. 996f
  2. ↑ Commentarius in Algorismum vulgarum , completed on July 31, 1291 in Bologna, published by Maximilian Curtze Petri Philomeni de Dacia in Algorismum vulgarem Johannis de Sacrobosco commentarius una cum algorismo ipso , Copenhagen 1897
  3. ↑ A. Otto Liber Daticus Roskildensis , Copenhagen 1933
  4. ↑ website for this
personal data
SURNAME Petrus de Dacia
ALTERNATIVE NAMES Petrus Dacus; Petrus Dacia; Peter Nightingale; Petrus de Dacia; Peter Danus; Petrus Philomena
BRIEF DESCRIPTION Danish mathematician and astronomer
DATE OF BIRTH 13th Century
DATE OF DEATH 14th Century