Christopher Clavius, (25 March 1538 – 6 February 1612ENCYCLOPEDIA.COM Clavius, Christoph
/ref>) was a

Jesuit The Society of Jesus (; abbreviation: S.J. or SJ), also known as the Jesuit Order or the Jesuits ( ; ), is a religious order (Catholic), religious order of clerics regular of pontifical right for men in the Catholic Church headquartered in Rom ...

German

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 ...

, head of mathematicians at the , and

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

who was a member of the Vatican commission that accepted the proposed calendar invented by

Aloysius Lilius Aloysius Lilius ( 1510 – 1576), also variously referred to as Luigi Lilio or Luigi Giglio, was an Italian physician, astronomer, philosopher and chronologist, and also the "primary author" who provided the proposal that (after modifications) ...

, that is known as the

Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...

. Clavius would later write defences and an explanation of the reformed calendar, including an emphatic acknowledgement of Lilius' work. In his last years, he was probably the most respected astronomer in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and his textbooks were used for astronomical education for over fifty years in and even out of Europe.

Early life

Little is known about Christopher Clavius' early life, with the only certain fact being that he was born in

Bamberg Bamberg (, , ; East Franconian German, East Franconian: ''Bambärch'') is a town in Upper Franconia district in Bavaria, Germany, on the river Regnitz close to its confluence with the river Main (river), Main. Bamberg had 79,000 inhabitants in ...

in either 1538 or 1537. His given name is not known to any great degree of certainty—it is thought by scholars to have perhaps been ''Christoph Clau'' or ''Klau''. There are also some who think that his taken name, ''Clavius'', may be a Latinization of his original German name, suggesting that his name may have been ''Schlüssel'' (German for 'key', which is ''clavis'' in Latin). Clavius joined the Jesuit order in 1555. He attended the

University of Coimbra The University of Coimbra (UC; , ) is a Public university, public research university in Coimbra, Portugal. First established in Lisbon in 1290, it went through a number of relocations until moving permanently to Coimbra in 1537. The university ...

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

, where it is possible that he had some kind of contact with the famous mathematician

Pedro Nunes Pedro Nunes (; Latin: ''Petrus Nonius''; 1502 – 11 August 1578) was a Portuguese mathematician, cosmographer, and professor, probably from a New Christian (of Jewish origin) family.Leitão, Henrique, "Para uma biografia de Pedro Nunes: O ...

(''Petrus Nonius''). Following this he went to Italy and studied theology at the Jesuit in

Rome Rome (Italian language, Italian and , ) is the capital city and most populated (municipality) of Italy. It is also the administrative centre of the Lazio Regions of Italy, region and of the Metropolitan City of Rome. A special named with 2, ...

. He was ordained in 1564, and 15 years later was assigned to compute the basis for a reformed calendar that would stop the slow process in which the Church's holidays were drifting relative to the seasons of the year. Using the Prussian Tables of Erasmus Reinhold and building on the work of

, he proposed a calendar reform that was adopted in 1582 in Catholic countries by order of

Pope Gregory XIII Pope Gregory XIII (, , born Ugo Boncompagni; 7 January 1502 – 10 April 1585) was head of the Catholic Church and ruler of the Papal States from 13 May 1572 to his death in April 1585. He is best known for commissioning and being the namesake ...

and is now the Gregorian calendar used worldwide. Within the Jesuit order, Clavius was almost single-handedly responsible for the adoption of a rigorous mathematics curriculum in an age where mathematics was often ridiculed by philosophers as well as fellow Jesuits like Benito Pereira. In

logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...

, Clavius' Law (inferring of the truth of a proposition from the inconsistency of its negation) is named after him. He used the

decimal point FIle:Decimal separators.svg, alt=Four types of separating decimals: a) 1,234.56. b) 1.234,56. c) 1'234,56. d) ١٬٢٣٤٫٥٦., Both a comma and a full stop (or period) are generally accepted decimal separators for international use. The apost ...

in the goniometric tables of his ''astrolabium'' in 1593 and he was one of the first who used it in this way in the West.

Astronomy

Clavius wrote a commentary on the most important astronomical textbook of the late Middle Ages, ''De Sphaera'' of Johannes de Sacrobosco. The commentary by Clavius was one of the most influential astronomy textbooks of its time and had at least 16 editions between 1570 and 1618, with Clavius himself revising the text seven times and in each case greatly expanding it. In the 1585 edition of his aforementioned commentary he located (independently of

Tycho Brahe Tycho Brahe ( ; ; born Tyge Ottesen Brahe, ; 14 December 154624 October 1601), generally called Tycho for short, was a Danish astronomer of the Renaissance, known for his comprehensive and unprecedentedly accurate astronomical observations. He ...

) the nova from 1572 in the

fixed stars In astronomy, the fixed stars () are the luminary points, mainly stars, that appear not to move relative to one another against the darkness of the night sky in the background. This is in contrast to those lights visible to the naked eye, name ...

sphere (in the constellation of

Cassiopeia Cassiopeia or Cassiopea may refer to: Greek mythology * Cassiopeia (mother of Andromeda), queen of Aethiopia and mother of Andromeda * Cassiopeia (wife of Phoenix), wife of Phoenix, king of Phoenicia * Cassiopeia, wife of Epaphus, king of Egy ...

) and found that the position of the nova was exactly the same for all observers. That meant that it had to be beyond the Moon, and the doctrine that the heavens could not change was proven false. As an astronomer Clavius adhered strictly to the

geocentric model In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded scientific theories, superseded description of the Universe with Earth at the center. Under most geocentric m ...

of the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

, in which all the heavens rotate about the

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

. Though he opposed the

heliocentric model Heliocentrism (also known as the heliocentric model) is a superseded astronomical model in which the Earth and planets orbit around the Sun at the center of the universe. Historically, heliocentrism was opposed to geocentrism, which placed th ...

Copernicus Nicolaus Copernicus (19 February 1473 – 24 May 1543) was a Renaissance polymath who formulated a mathematical model, model of Celestial spheres#Renaissance, the universe that placed heliocentrism, the Sun rather than Earth at its cen ...

, he recognized problems with the Ptolemaic model. He was treated with great respect by

Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

, who visited him in 1611 and discussed the new observations being made with the

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

; Clavius had by that time accepted the new discoveries as genuine, though he retained doubts about the reality of the mountains on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

and said he could not see the four Jupiter's satellites through the telescope. Later, a large crater on the Moon was named in his honor.

Collegio Romano

During his time at Collegio Romano Clavius served as the head of the

s, a public professor of mathematics, and as the Director of Advanced Instruction and Research at the Academy of Mathematics until 1610 in an official capacity and for two more years until 1612 in an informal role. The Academy existed in an informal capacity for many years before Clavius' arrival in Rome in 1561. However, in 1580 in his document titled ''Ordo servandus in addiscendis disciplinis mathematicis,'' Clavius described a detailed curriculum for mathematics to have the College officially recognize the Academy. The curriculum he proposed contained three different curricula aiming to educate new Jesuits in mathematics. The curriculum contained three different courses: one year, a two-year, and a three-year. The course material to be covered were

optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...

statics Statics is the branch of classical mechanics that is concerned with the analysis of force and torque acting on a physical system that does not experience an acceleration, but rather is in mechanical equilibrium, equilibrium with its environment ...

, astronomy, and

acoustics Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician ...

, emphasizing mathematics. His request was eventually denied, but nonetheless he was given the title of Professor of Mathematics. Clavius made another attempt in 1586 to establish the Academy as an official course at the Collegio Romano, but there was opposition from the philosophers at the College. The Academy remained an unofficial curriculum until 1593 or 1594. Upon its eventual founding, the Academy required nomination by the Professor of Mathematics for admission. Clavius taught the advanced course within the Academy, but little is known about his specific teachings and work as a professor during his time at the College. The exact number of students that Clavius taught is unclear, but in a letter from Christoph Grienberger to Clavius in 1595, it is stated that at that time, Clavius had around ten students. The exact structure of the courses and how they were taught is unclear. There has been no evidence to show whether the students he taught shared classes or the specific material he chose to cover. The purpose for founding the Academy was to train technical specialists, to expand the pedagogical corps to support the growing need for professors, as the number of colleges at the time was rapidly increasing, as well as the training of missionaries in order to support their efforts in remote places. With the purpose of the Academy clear, most of what Clavius and his students did in the Academy is unknown. This lack of detailed information has led to most of what Clavius did during his years at the College falling into obscurity. Clavius and Galileo Galilei often shared correspondence during his time at the College, discussing proofs and theories. It is likely that while running the Academy, he was also writing to Galileo and sharing his notes from the College's logic course to help Galileo in his endeavors to be able to adequately explain and demonstrate his ideas to others, which is something Galileo had struggled with in the past, specifically when trying to convince Clavius of his methods. Following his death in 1612, informal courses in the Academy continued at the College. However, due to the lack of mention of mathematicians in the College's catalog after 1615, it appears the Academy's official recognition by the Collegio Romano ended soon after Christopher Clavius's death.

Selected works

* Commentary on Euclid, 1574
''Gnomonices libri octo''
1581 reatise of gnomonics">gnomonics.html" ;"title="reatise of gnomonics">reatise of gnomonics* * ''Novi calendarii romani apologia''. Rome, 1588
''Astrolabium''
Rome, 1593 * * ''Romani calendarii a Gregorio XIII P.M. restituti explicatio''. Rome, 1603 (An explanation of the Gregorian calendar) **
Romani calendarii a Gregorio XIII P.M. restituti explicatio
'. (European Cultural Heritage Online) **
Romani calendarii a Gregorio XIII P.M. restituti explicatio
'. (University of Notre Dame) * ''Refutatio cyclometriae Joseph Justus Scaliger, Iosephi Scaligeri''. Mainz, 1609 *
Elementorum Libri XV
'. Cologne, 1627 (Published online by the Sächsischen Landesbibliothek - Staats- und Universitätsbibliothek Dresden) * (Critical edition of his correspondence) Clavius' complete mathematical works (5 volumes, Mainz, 1611–1612) ar
available online
.

References

Bibliography

* Ralf Kern, ''Wissenschaftliche Instrumente in ihrer Zeit''. Cologne, 2010. pp. 254 – 255. * * * * Christoph Clavius, ''Corrispondenza'', Edizione critica a cura di Ugo Baldini e Pier Daniele Napolitani, 7 volumes, Edizioni del Dipartimento di Matematica dell'Università di Pisa, Pisa, 1992

External links

*
Christopher Clavius (1537-1612)
The Galileo Project *

* ttp://www.unigre.it/archivioimg/Fondo_Curia_2009/Indice_Autori.htm Cristoforo Clavioin th
Historical Archives of the Pontifical Gregorian University
* Project Clavius On The Web
A Web platform for the works and literature of Christophorus Clavius
CNR-IIT, CNR-ILC, APUG {{DEFAULTSORT:Clavius, Christopher 1538 births 1612 deaths People from Bamberg 16th-century German astronomers 16th-century German Jesuits German scientific instrument makers University of Coimbra alumni Gregorian calendar 16th-century German mathematicians 17th-century German mathematicians Jesuit scientists 17th-century German astronomers