Johannes de Sacrobosco

Johannes de Sacrobosco or Sacro Bosco (John of Holywood, c. 1195 – c. 1256) was an English scholar and astronomer/astrologer who taught at the University of Paris and wrote the authoritative mediaeval astronomy text "Tractatus de Sphaera".

Although described as English, his birthplace is unknown because Sacrobosco is an otherwise unknown town or region. The traditional belief that he was born in Halifax is now considered discredited because Halifax [CathEncy|url=http://en.wikisource.org/wiki/Catholic_Encyclopedia_(1913)/Joannes_de_Sacrobosco|title=Joannes de Sacrobosco] means 'holy hair', not 'holy wood'Fact|date=December 2007. However, there is good reason to believe the 'holy wood' to which reference is being made is one of two found in IrelandFact|date=October 2008. The most noted of the two is an ecclesiastical centre in County Down founded in the mid-seventh century. This would also lend credence to a belief that he was of Irish origins. He was educated at Oxford University. According to a seventeenth century account, he arrived at the University of Paris on June 5, 1221, but whether as an arts student or as a licentiate (one having a Master of Arts degree from another university and thus qualified to teach) is unclear. [Olaf Pedersen, "In Quest of Sacrobosco," "Journal for the History of Astronomy", 16(1985): 175-182.] In due course, he began to teach the mathematical disciplines at the University of Paris. About 1230, his most well known work, "Tractatus de Sphaera", was published. In this book, Sacrobosco discussed the Earth and its place in the Universe. It was required reading by students in all Western European universities for the next four centuries. Its description of the Earth as a sphere and its popularity exposes the nineteenth-century opinion that medieval scholars thought the Earth was flat as a fabrication (See: Flat Earth). In his "Algorismus", theorized to have been his first work, Sacrobosco showed himself to be a strong proponent of Arab methods of mathematics, his "Algorismus" being the first text to introduce Hindu-Arabic numerals and procedures into the university curriculum. [Olaf Pedersen, "In Quest of Sacrobosco," "Journal for the History of Astronomy", 16(1985): 199-200.]

What Sacrobosco may be most famous for is his criticism of the Julian calendar. In his book on computus, "De Anni Ratione" (1235), he maintained that the Julian calendar was ten days off and that some correction was needed. He made no proposal to correct the accumulated error of ten days but looking to the future, he proposed to leave one day out of the calendar every 288 years. [Olaf Pedersen, "In Quest of Sacrobosco," "Journal for the History of Astronomy", 16(1985): 209-10.] In this book, he invented the false notion that Caesar Augustus took a day from February to give to August (see Julian calendar).Fact|date=February 2007

The year of his death is uncertain, with evidence supporting the years 1234, 1236, 1244, and 1256. [Olaf Pedersen, "In Quest of Sacrobosco," "Journal for the History of Astronomy", 16(1985): 186-9, 192.] The inscription marking his burial place in the monastery of Saint-Mathurin in Paris described him as a computist, who was an expert on the reckoning of time. [Olaf Pedersen, "In Quest of Sacrobosco," "Journal for the History of Astronomy", 16(1985): 181.] :M. Christi bis C. quarto deno quarter anno:De Sacro Bosco discrevit tempora ramus,:Gratia cui dederat nomen divina Johannes:

The lunar crater Sacrobosco is named after him.

Works

* "Tractatus de Sphæra"
* "Algorismus', or "De Arte numerandi", printed without date or place [1490?] , and at Vienna, 1517, by Hieronymus Vietor; Cracow, 1521 or 1522; and Venice, 1523
* "De Anni Ratione", or "De Computo Ecclesiastico", printed, Paris [1538?] , 1550, 1572, 8vo.

Notes

References

* Pedersen, Olaf. "In Quest of Sacrobosco." "Journal for the History of Astronomy", 16 (1985): 175-221.
*

External links

* [http://www.hps.cam.ac.uk/starry/sacrobosco.html Johannes de Sacrobosco]