: ''For the English patristic scholar and Benedictine abbot, see Jacques de Billy (abbot) (1535–1581).'' Jacques de Billy (March 18, 1602 – January 14, 1679) was a French Jesuit

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

. Born in

Compiègne Compiègne (; pcd, Compiène) is a commune in the Oise department in northern France. It is located on the river Oise. Its inhabitants are called ''Compiégnois''. Administration Compiègne is the seat of two cantons: * Compiègne-1 (with 19 ...

, he subsequently entered the

Society of Jesus , image = Ihs-logo.svg , image_size = 175px , caption = ChristogramOfficial seal of the Jesuits , abbreviation = SJ , nickname = Jesuits , formation = , founders ...

. From 1629 to 1630, Billy taught mathematics at the Jesuit College at Pont-à-Mousson. He was still studying

theology Theology is the systematic study of the nature of the divine and, more broadly, of religious belief. It is taught as an academic discipline, typically in universities and seminaries. It occupies itself with the unique content of analyzing th ...

at this time. From 1631 to 1633, Billy taught mathematics at the Jesuit college at

Rheims Reims ( , , ; also spelled Rheims in English) is the most populous city in the French department of Marne, and the 12th most populous city in France. The city lies northeast of Paris on the Vesle river, a tributary of the Aisne. Founded b ...

. From 1665 to 1668 he was professor of mathematics at the Jesuit college at

Dijon Dijon (, , ) (dated) * it, Digione * la, Diviō or * lmo, Digion is the prefecture of the Côte-d'Or department and of the Bourgogne-Franche-Comté region in northeastern France. the commune had a population of 156,920. The earl ...

. One of his pupils there was Jacques Ozanam. Billy also taught in

Grenoble lat, Gratianopolis , commune status = Prefecture and commune , image = Panorama grenoble.png , image size = , caption = From upper left: Panorama of the city, Grenoble’s cable cars, place Saint- ...

. He also served as

rector Rector (Latin for the member of a vessel's crew who steers) may refer to: Style or title *Rector (ecclesiastical), a cleric who functions as an administrative leader in some Christian denominations *Rector (academia), a senior official in an edu ...

of a number of Jesuit Colleges in

Châlons-en-Champagne Châlons-en-Champagne () is a city in the Grand Est region of France. It is the capital of the department of Marne, despite being only a quarter the size of the city of Reims. Formerly called Châlons-sur-Marne, the city was officially renam ...

Langres Langres () is a commune in northeastern France. It is a subprefecture of the department of Haute-Marne, in the region of Grand Est. History As the capital of the Romanized Gallic tribe known as the Lingones, it was called Andematunnum, then L ...

and in

Sens Sens () is a commune in the Yonne department in Bourgogne-Franche-Comté in north-central France, 120 km from Paris. Sens is a sub-prefecture and the second city of the department, the sixth in the region. It is crossed by the Yonne and t ...

. The mathematician Claude Gaspard Bachet de Méziriac, who had been a pupil of Billy's at Rheims, became a close friend. Billy maintained a correspondence with the mathematician

Pierre de Fermat Pierre de Fermat (; between 31 October and 6 December 1607 – 12 January 1665) was a French mathematician who is given credit for early developments that led to infinitesimal calculus, including his technique of adequality. In particular, he ...

Work and legacy

Billy produced a number of results in

number theory Number theory (or arithmetic or higher arithmetic in older usage) is a branch of pure mathematics devoted primarily to the study of the integers and integer-valued functions. German mathematician Carl Friedrich Gauss (1777–1855) said, "Math ...

which have been named after him. Bachet introduced Billy to

indeterminate analysis In mathematics, a Diophantine equation is an equation, typically a polynomial equation in two or more unknowns with integer coefficients, such that the only solutions of interest are the integer ones. A linear Diophantine equation equates t ...

. Billy's mathematical works include ''

Diophantus Diophantus of Alexandria ( grc, Διόφαντος ὁ Ἀλεξανδρεύς; born probably sometime between AD 200 and 214; died around the age of 84, probably sometime between AD 284 and 298) was an Alexandrian mathematician, who was the aut ...

Redivivus''. In the field of

astronomy Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...

, he published several astronomical tables. First published in

by Pierre Palliot in 1656, Billy's tables of

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 is called ''Tabulae Lodoicaeae seu universa eclipseon doctrina tabulis, praeceptis ac demonstrationibus explicata. Adiectus est calculus, aliquot eclipseon solis & lunae, quae proxime per totam Europam videbuntur''. The tables were calculated for the years 1656 to 1693. This work also contains solar and lunar tables based on the

Paris meridian The Paris meridian is a meridian line running through the Paris Observatory in Paris, France – now longitude 2°20′14.02500″ East. It was a long-standing rival to the Greenwich meridian as the prime meridian of the world. The "Paris merid ...

. It also includes a detailed examination of problems involved in astronomical calculations. Billy was one of the first scientists to reject the role of

astrology Astrology is a range of divinatory practices, recognized as pseudoscientific since the 18th century, that claim to discern information about human affairs and terrestrial events by studying the apparent positions of celestial objects. Di ...

in science. He also rejected old notions about the malevolent influence of

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or Coma (cometary), coma, and sometimes also a Comet ta ...

s. He died at

. The crater Billy on the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...

is named after him. File:De Billy, Jacques – Diophantus redivivus, 1670 – BEIC 18285.jpg, ''Diophantus redivivus'', 1670

References

*
Moon Watch

Work and legacy

See also

References

Further reading