Petrus de Dacia (mathematician)

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

Life

His year of birth and place of birth is unknown. He was originally a canon of the cathedral of Roskilde. He first appears in a letter of the German Dominican Provincial Hermann von Minden ( from the period 1286-1290 ), which thanks him for the gift of some astronomical instruments and suggests him to leave Italy and to visit Germany. 1291-1292 it is occupied as a professor at the University of Bologna, where he taught mathematics and astronomy. 1292 he is in Paris and is very active there in 1293 as an author. Then we lose track to 1303, where he is detectable in Roskilde again because of a letter from Pope Boniface VIII (4 July 1303). Since he does not appear in the obituaries of the Cathedral of Roskilde, he probably died out.

He should not be confused with Peter of Dacia, a Swedish Dominican same name. Then already pointed H. Schück 1895 back, he was nevertheless repeatedly in the literature confused with this. He is also not to be confused with another Petrus de Dacia, which was 1326/1327 Rector of the University of Paris.

Work

From Peter Dacus over 200 manuscripts mathematical and astronomical contents are obtained ( Olaf Pedersen ), some of uncertain attribution. Below is a commentary on the arithmetic textbook by Sacrobosco, in which there are also original contributions from Peter Dacus about over the drawing of cube roots. Another work is an astronomical calendar for the years 1292 to 1369 (76 years), he as a replacement for the outdated calendar of Robert Grosseteste wrote in Paris ( with improvements over Grosseteste for the phases of the moon ). In the appendix he gives instructions for customizing the calendar for the years 1369 and 1442nd His calendar remained in use for over 150 years. The calendar has the particularity that it the maximum position of the sun and the day length listed for each day, which was after Alfred Otto also the approach of an unknown astronomers in the partially preserved Calendar Liber daticus 1274 the Cathedral of Roskilde, which probably served as a model.

Its on the number of surviving manuscripts of (68 ) most popular work is his lunar tables ( tab- lune ).

Another important contribution is his manuscripts on astronomical instruments. Among the Tractatus de Semissis (Paris, 1293, preserved in 10 manuscripts ), who comes from a Peter of St. Omer ( Petrus de St. Audomaro ) and was written in Paris in 1293. This is very likely according to Olaf Pedersen Peter Dacus identical. The treatise describes the author strongly against the instrument of Campanus of Novara ( 1260 ) improved Equatorium to determine the lengths of the planets in the zodiac. A similar instrument has not survived, but was reconstructed by Olaf Pedersen 1967.

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

In Tractatus eclipsorii he describes a Equatorium to determine eclipses. As in other manuscripts, the data refer to the geographical position of Paris.