Johannes de Sacrobosco
Encyclopedia
Johannes de Sacrobosco or Sacro Bosco (John of Holywood, c. 1195 – c. 1256) was a scholar, monk
Monk
A monk is a person who practices religious asceticism, living either alone or with any number of monks, while always maintaining some degree of physical separation from those not sharing the same purpose...

, and astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

 (probably English
English people
The English are a nation and ethnic group native to England, who speak English. The English identity is of early mediaeval origin, when they were known in Old English as the Anglecynn. England is now a country of the United Kingdom, and the majority of English people in England are British Citizens...

, but possibly Irish
Irish people
The Irish people are an ethnic group who originate in Ireland, an island in northwestern Europe. Ireland has been populated for around 9,000 years , with the Irish people's earliest ancestors recorded having legends of being descended from groups such as the Nemedians, Fomorians, Fir Bolg, Tuatha...

 or Scottish
Scottish people
The Scottish people , or Scots, are a nation and ethnic group native to Scotland. Historically they emerged from an amalgamation of the Picts and Gaels, incorporating neighbouring Britons to the south as well as invading Germanic peoples such as the Anglo-Saxons and the Norse.In modern use,...

) who taught at the University of Paris
University of Paris
The University of Paris was a university located in Paris, France and one of the earliest to be established in Europe. It was founded in the mid 12th century, and officially recognized as a university probably between 1160 and 1250...

 and wrote the authoritative mediaeval astronomy text Tractatus de Sphaera.

Origins

Although described as English, his birthplace is unknown because Sacrobosco is an otherwise unknown town or region. The belief on his nationality is based on a 1271 statement by Robertus Anglicus
Robertus Anglicus
Robertus Anglicus was an English astronomer of the thirteenth century. He taught at the University of Montpellier, and possibly also at Paris. He is known as the author of a 1271 commentary on the De Sphera Mundi of Johannes de Sacrobosco. It includes a significant reference to the state of the...

. Traditional theories were based on suggestions of antiquarians, without documentary proof.

Sacrobosco is also called John of Holywood, by reverse etymology
Etymology
Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

 from the Latin sacro bosco. A traditional belief, that he was born in Halifax
Halifax, West Yorkshire
Halifax is a minster town, within the Metropolitan Borough of Calderdale in West Yorkshire, England. It has an urban area population of 82,056 in the 2001 Census. It is well-known as a centre of England's woollen manufacture from the 15th century onward, originally dealing through the Halifax Piece...

, is due to the 16th century author, John Leland, and was discredited by William Camden
William Camden
William Camden was an English antiquarian, historian, topographer, and officer of arms. He wrote the first chorographical survey of the islands of Great Britain and Ireland and the first detailed historical account of the reign of Elizabeth I of England.- Early years :Camden was born in London...

: Halifax means 'holy hair', not 'holy wood'. Sacrobosco has been identified, by Thomas Dempster
Thomas Dempster
Thomas Dempster was a Scottish scholar and historian. Born into the aristocracy in Aberdeenshire, which comprises regions of both the Scottish highlands and the Scottish lowlands, he was sent abroad as a youth for his education. The Dempsters were Catholic in an increasingly Protestant country and...

, with an Augustinian canon from Holywood Abbey, Nithsdale
Nithsdale
Nithsdale , also known by its anglicised gaelic name Strathnith or Stranit, is the valley of the River Nith in Scotland, and the name of the region...

 (in fact a Premonstratensian
Premonstratensian
The Order of Canons Regular of Prémontré, also known as the Premonstratensians, the Norbertines, or in Britain and Ireland as the White Canons , are a Catholic religious order of canons regular founded at Prémontré near Laon in 1120 by Saint Norbert, who later became Archbishop of Magdeburg...

 house); which would be a reason for presuming him a Scot. He is also claimed by Holywood, County Down, this being based on a suggestion of Richard Stanihurst. However, Pederson attributes this assertion to Holywood being known to Stanihurst. Pedersons book mentioned that in 1639 James Ware assumed that the birthplace of Sacrobosco was near Dublin. Stanihurst and even Pederson were probably unaware that the seat of the Sacrobosco/Hollywood family in Ireland was in Artane, a suburb of Dublin ("The History of the County of Dublin" by John D'Alton published in 1838). Local historical records in Ireland seem to indicate that Sacrobosco was a member of the Artane Hollywoods and was born in Artane Castle. A similar claim is made for Holywood, County Wicklow
County Wicklow
County Wicklow is a county in Ireland. It is part of the Mid-East Region and is also located in the province of Leinster. It is named after the town of Wicklow, which derives from the Old Norse name Víkingalág or Wykynlo. Wicklow County Council is the local authority for the county...

, though there is no known historical document which supports this.

Life

The story that he was educated at the University of Oxford
University of Oxford
The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...

 is no more documented than the stories on his origin.

According to a seventeenth century account, he arrived at the University of Paris on 5 June 1221, but whether as an arts student or as a licentiate
Licentiate
Licentiate is the title of a person who holds an academic degree called a licence. The term may derive from the Latin licentia docendi, meaning permission to teach. The term may also derive from the Latin licentia ad practicandum, which signified someone who held a certificate of competence to...

 (one having a Master of Arts
Master of Arts (postgraduate)
A Master of Arts from the Latin Magister Artium, is a type of Master's degree awarded by universities in many countries. The M.A. is usually contrasted with the M.S. or M.Sc. degrees...

 degree from another university and thus qualified to teach) is unclear. In due course, he began to teach the mathematical disciplines at the University of Paris.

The year of his death is uncertain, with evidence supporting the years 1234, 1236, 1244, and 1256. The inscription marking his burial place in the monastery of Saint-Mathurin in Paris described him as a computist, one who was an expert on the calculation of Easter.
M. Christi bis C. quarto deno quarter anno
De Sacro Bosco discrevit tempora ramus,
Gratia cui dederat nomen divina Johannes:


The lunar crater Sacrobosco
Sacrobosco (crater)
Sacrobosco is an irregular lunar impact crater that is located in the rugged southern highlands to the west of the Rupes Altai escarpment. It is a readily identified feature due to the three circular craters that lie on its floor. The rim of Sacrobosco is heavily worn and eroded, especially in the...

 is named after him.

Tractatus de Sphaera

About 1230, his best known work, Tractatus de Sphaera, was published. In this book, Sacrobosco gives a readable account of the Ptolemaic universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

. It was required reading by students in all Western European universities for the next four centuries. Though principally about the heavens it contains a clear description of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 as a sphere and its popularity shows the nineteenth-century opinion that medieval scholars after this date thought the Earth was flat as a fabrication (See: Flat Earth
Flat Earth
The Flat Earth model is a belief that the Earth's shape is a plane or disk. Most ancient cultures have had conceptions of a flat Earth, including Greece until the classical period, the Bronze Age and Iron Age civilizations of the Near East until the Hellenistic period, India until the Gupta period ...

).

Algorismus

In his Algorismus
Algorismus
Algorismus refers to:* The various 13th century Latin writings on the methods numerical calculation, using the then newly introduced Hindu-Arabic numerals. Well known authors who wrote about the topic are Alexander de Villa Dei and Johannes de Sacrobosco...

, theorized to have been his first work, Sacrobosco showed himself to be a strong proponent of the Arab
Arab
Arab people, also known as Arabs , are a panethnicity primarily living in the Arab world, which is located in Western Asia and North Africa. They are identified as such on one or more of genealogical, linguistic, or cultural grounds, with tribal affiliations, and intra-tribal relationships playing...

 methods of numerical calculation, his Algorismus being the first text to introduce Hindu-Arabic numerals
Arabic numerals
Arabic numerals or Hindu numerals or Hindu-Arabic numerals or Indo-Arabic numerals are the ten digits . They are descended from the Hindu-Arabic numeral system developed by Indian mathematicians, in which a sequence of digits such as "975" is read as a numeral...

 and procedures into the European university curriculum.

On the calendar

What Sacrobosco may be most famous for is his criticism of the Julian calendar
Julian calendar
The Julian calendar began in 45 BC as a reform of the Roman calendar by Julius Caesar. It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year .The Julian calendar has a regular year of 365 days divided into 12 months...

. In his book on computus
Computus
Computus is the calculation of the date of Easter in the Christian calendar. The name has been used for this procedure since the early Middle Ages, as it was one of the most important computations of the age....

, 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. In this book, he invented the false notion that Caesar Augustus took a day from February to give to August (see Julian calendar).

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.
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