Petrus de Dacia, also called Philomena and Peder Nattergal (Peter Nightingale), was a

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish a ...

scholar who lived in the 13th century. He worked mainly in

Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. S ...

and

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...

, writing in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

. He published a calendar of

new moon In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse. ...

dates for the years 1292-1367. In 1292, he published a book on mathematics that contained a new method for the calculation of

cubic root In mathematics, a cube root of a number is a number such that . All nonzero real numbers, have exactly one real cube root and a pair of complex conjugate cube roots, and all nonzero complex numbers have three distinct complex cube roots. Fo ...

s. He also described a mechanical instrument to predict solar and lunar

eclipse An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three ce ...

s as seen from Paris.

Editions

*''Corpus Philosophorum Danicorum Medii Aevi'' vol. X, ed. Fritz Saaby Pedersen. Copenhagen 1983.
''Petri Philomeni de Dacia in Algorismum vulgarem Johannis de Sacrobosco commentarius''
edited by Maximilian Curtze, year 1897. This text by Petrus Philomena de Dacia is a commentary about elementary methods in arithmetic. Its primary notability is that it has a better method for extracting cube roots (better than the pre-existing method reported by

Johannes de Sacrobosco Johannes de Sacrobosco, also written Ioannes de Sacro Bosco, later called John of Holywood or John of Holybush ( 1195 – 1256), was a scholar, monk, and astronomer who taught at the University of Paris. He wrote a short introduction to the Hi ...

References

*Pedersen, Olaf (in: Complete Dictionary of Scientific Biography. 2008. http://www.encyclopedia.com/doc/1G2-2830903368.html) *Rasch, G. (1932) Petrus de Dacia, pp. 12-15 in: Meisen, V. ''Prominent Danish Scientists through the Ages.'' University Library of Copenhagen 450th Anniversary. Levin & Munksgaard, Copenhagen {{DEFAULTSORT:Petrus de Dacia 13th-century mathematicians Danish mathematicians Danish science writers Danish scientific instrument makers 13th-century Danish people