Christopher Clavius
Jesuit astronomer and mathematician who shaped the Gregorian calendar.
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Christopher Clavius was a Jesuit German mathematician, physicist, and astronomer who served as head of mathematicians at the Collegio Romano. He was a member of the Vatican commission that accepted the calendar reform proposed by Aloysius Lilius, which became known as the Gregorian calendar. Clavius later wrote defences and explanations of the reformed calendar, acknowledging Lilius' work, and in his later years was probably the most respected astronomer in Europe. His textbooks were used for astronomical education for over fifty years in and even out of Europe.
Quick Facts
- Born
- 25 March 1538
- Birthplace
- Bamberg, Bavaria, Holy Roman Empire
- Died
- 6 February 1612
- Place of death
- Rome, Papal States
- Field
- Mathematics, astronomy
- Education
- University of Coimbra; Collegio Romano
- Known for
- Gregorian calendar; Clavius' Law
- Honorific prefix
- The Reverend
Facts from the source article.
Early life
Little is known about Christopher Clavius’s early years, except that he was born in Bamberg around 1537 or 1538. His birth name is uncertain; scholars think it may have been Christoph Clau or Klau, and some believe Clavius is a Latinized version of the German Schlüssel, meaning key. He entered the Jesuit order in 1555, studied at the University of Coimbra in Portugal—where he may have met the mathematician Pedro Nunes—and then moved to Italy to study theology at the Collegio Romano in Rome. Ordained in 1564, he was assigned fifteen years later to help fix the calendar, as Church holidays were drifting relative to the seasons. Building on Aloysius Lilius’s work and using Erasmus Reinhold’s Prussian Tables, he proposed a reform adopted in 1582 by Pope Gregory XIII in Catholic countries, now known as the Gregorian calendar. Clavius later defended and explained the new calendar, giving full credit to Lilius. Within the Jesuit order, he was largely responsible for introducing a rigorous mathematics curriculum at a time when mathematics was often dismissed by philosophers and even fellow Jesuits like Benito Pereira. The logical principle known as Clavius’s Law—inferring a proposition’s truth from the inconsistency of its negation—is named after him. In 1593, he used the decimal point in the goniometric tables of his astrolabium, making him one of the first in the West to do so. As an astronomer, Clavius wrote a widely used commentary on Johannes de Sacrobosco’s De Sphaera, revised seven times and printed in at least sixteen editions. In its 1585 edition, he independently located the 1572 nova in the fixed stars of Cassiopeia, showing it was beyond the Moon and disproving the idea that the heavens were unchanging. He adhered to the geocentric model but recognized problems with Ptolemy’s system. Galileo visited him in 1611; Clavius accepted the new telescopic discoveries, though he doubted lunar mountains and could not see Jupiter’s moons. A large lunar crater bears his name. At the Collegio Romano, he served as head of mathematicians and directed the Academy of Mathematics, proposing a detailed curriculum in 1580 that was initially denied but eventually established around 1593 or 1594. By his later years, he was likely the most respected astronomer in Europe, and his textbooks shaped astronomical education for over fifty years.
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) the nova from 1572 in the fixed stars sphere (in the constellation of Cassiopeia) 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 of the Solar System, in which all the heavens rotate about the Earth. Though he opposed the heliocentric model of Copernicus, he recognized problems with the Ptolemaic model. He was treated with great respect by Galileo, who visited him in 1611 and discussed the new observations being made with the telescope; Clavius had by that time accepted the new discoveries as genuine, though he retained doubts about the reality of the mountains on the Moon 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 mathematicians, 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, statics, astronomy, and acoustics, 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.
Frequently Asked Questions
When and where was Christopher Clavius born?
Christopher Clavius was born on 25 March 1538 in Bamberg, Bavaria, Holy Roman Empire.
When did Christopher Clavius die?
Christopher Clavius died on 6 February 1612 in Rome, Papal States.
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