Regiomontanus [Lat.,=belonging to the royal mountain, i.e., to Königsberg], 1436-76, German astronomer and mathematician, b. Königsberg. His original name was Johannes Müller. In 1461 he went to Rome with Cardinal Bessarion and learned Greek in order to translate Greek writings. In 1468 he was called to the court of the king of Hungary to make a collection of Greek manuscripts, and three years later he settled at Nuremberg, where, with his pupil and patron, Bernhard Walther, he established an observatory and a printing press. Among other works they published the Ephemerides for the years 1474-1506, calculated by Regiomontanus, and Georg von Purbach's Theoricae planetarum novae. Summoned by Pope Sixtus IV, Regiomontanus went to Rome in 1475 to assist in reforming the calendar and was made bishop of Regensburg. He died in Rome. He made improved instruments, both mathematical and astronomical, introduced algebra into Germany, and did much to further trigonometry.

Johannes Müller von Königsberg (June 6, 1436 – July 6, 1476), known by his Latin pseudonym Regiomontanus, was an important German mathematician, astronomer and astrologer.

He was born in the Franconian village of Unfinden near Königsberg, Bavaria, not in the more famous Königsberg in East Prussia.

Thus, he is also called Johannes Müller, der Königsberger (Johannes Müller of Königsberg). His full Latin name was Joannes de Regio monte, which abbreviated to Regiomontanus (from the Latin for "Königsberg"—"King's Mountain").

Life

At eleven years of age, he became a student at the university in Leipzig, Saxony. Three years later he continued his studies at Alma Mater Rudolfina, the university in Vienna, Austria. There he became a pupil and friend of Georg von Peurbach. In 1457 he graduated with a degree of "magister artium" (Master of Arts) and held lectures in optics and ancient literature. He built astrolabes for Matthias Corvinus of Hungary and Cardinal Bessarion, and in 1465 a portable sundial for Pope Paul II. His work with Peurbach brought him to the writings of Nicholas of Cusa (Cusanus), who held a heliocentric view. Regiomontanus, however, remained a geocentrist after Ptolemy. Following Peurbach's death, he continued the translation of Ptolemy's Almagest which Peurbach had begun at the initiative of Basilios Bessarion. From 1461 to 1465 Regiomontanus lived and worked at Cardinal Bessarion's house in Rome. He wrote De Triangulis omnimodus (1464) and Epytoma in almagesti Ptolemei. De Triangulis (On Triangles) was one of the first textbooks presenting the current state of trigonometry and included lists of questions for review of individual chapters. In it he wrote:

"You who wish to study great and wonderful things, who wonder about the movement of the stars, must read these theorems about triangles. Knowing these ideas will open the door to all of astronomy and to certain geometric problems."

In the Epytoma he critiqued the translation, pointing out inaccuracies. Later Nicolaus Copernicus would refer to this book as an influence on his own work. In 1467 Regiomontanus left Rome to work at the court of Matthias Corvinus of Hungary. There he calculated extensive astronomical tables and built astronomical instruments.

In 1471 he moved to the Free City of Nuremberg, in Franconia, then one of the Empire's important seats of learning, publication, commerce and art. He associated with the humanist and merchant Bernhard Walther who sponsored the observatory and the printing press. Regiomontanus remains famous for having built at Nuremberg the first astronomical observatory in Germany. In 1472 he published the first printed astronomical textbook, the "Theoricae novae Planetarum" of his teacher Georg von Peurbach. Peurbach worked at the Observatory of Großwardein (Oradea) in Transylvania, the first in Europe, and established in his "Tabula Varadiensis" this Transylvanian town's observatory as lying on the prime meridian of Earth.

In 1475 he went to Rome to work with Pope Sixtus IV on calendar reform. On the way he could publish his "Ephemeris" in Venice. Regiomontanus died mysteriously in Rome, July 61476, a month after his fortieth birthday. Some say he died of plague, others by (more likely) assassination.

A prolific author, Regiomontanus was internationally famous already in his lifetime. Despite having completed only a quarter of what he had intended to write, he left a substantial body of work. Domenico Maria Novara da Ferrara, the teacher of Nicolaus Copernicus, referred to Regiomontanus as having been his own teacher.

It is not true that he came to be called posthumously after the place of his birth, Königsberg/Bavaria (in Latin, Regiomontanus). In Regiomontanus' day it was common for scholars to Latinize their names when publishing.

He is known for having built one of the most famous automata, the wooden eagle of Regiomontanus, which flew from the city of Königsberg to meet the emperor, saluted him, and returned. He also built an iron fly of which it is said it flew out of Regiomontanus's hands at a feast, and taking a round, returned to him.

In 1561, Daniel Santbech compiled a collected edition of the works of Regiomontanus, De triangulis planis et sphaericis libri quinque (first published in 1533) and Compositio tabularum sinum recto, as well as Santbech's own Problematum astronomicorum et geometricorum sectiones septem. It was published in Basel by Henrich Petri and Petrus Perna.

Regiomontanus crater, on the Moon, is named after him.

Astrology

One biographer has claimed to have detected a decline in Regiomontanus' interest in astrology over his life, and came close to asserting that Regiomontanus had rejected it altogether. But more recent commentators have suggested that the occasional expression of skepticism about astrological prognostication reflected a disquiet about the procedural rigour of the art, not about its underlying principles. It seems plausible that, like some other astronomers, Regiomontanus concentrated his efforts on mathematical astronomy because he felt that astrology could not be placed on a sound footing until the celestial motions had been modeled accurately.

In his youth, Regiomontanus had cast horoscopes (natal charts) for famous patrons. His Tabulae directionum, completed in Hungary, were designed for astrological use and contained a discussion of different ways of determining astrological houses. The calendars for 1475-1531 which he printed at Nuremberg contained only limited astrological information—a method of finding times for bloodletting according to the position of the moon; subsequent editors added material.

But perhaps the works most indicative of Regiomontanus' hopes for an empirically sound astrology were his almanacs or ephemerides, produced first in Vienna for his own benefit, and printed in Nuremberg for the years 1475-1506. Weather predictions and observations were juxtaposed by Regiomontanus in his manuscript almanacs, and the form of the printed text enabled scholars to enter their own weather observations in order to likewise check astrological predictions; extant copies reveal that several did so. Regiomontanus' Ephemeris would be used in 1504, by a Christopher Columbus stranded on Jamaica, to intimidate the natives into continuing to provision him and his crew from their scanty food stocks, when he successfully predicted a lunar eclipse for February 29, 1504.

Regiomontanus did not live to produce the special commentary to the ephemerides that he had promised would reveal the advantages the almanacs held for the multifarious activities of physicians, for human births and the telling of the future, for weather forecasting, for the inauguration of employment, and for a host of other activities, although this lack was again made good by subsequent editors. Nevertheless Regiomontanus' promise suggests that he either was as convinced of the validity and utility of astrology as his contemporaries, or was willing to set aside his misgivings for the sake of commercial success.

Criticism

Gerolamo Cardano noted that much of the material of Regiomontanus on spherical trigonometry was plagiarised from the twelfth-century work of the Jabir ibn Aflah

Notes

Literature

• Irmela Bues, Johannes Regiomontanus (1436-1476). In: Fränkische Lebensbilder 11. Neustadt/Aisch 1984, S. 28 - 43
• Rudolf Mett: Regiomontanus. Wegbereiter des neuen Weltbildes. Teubner / Vieweg, Stuttgart / Leipzig 1996, ISBN 3-8154-2510-7
• Helmuth Gericke: Mathematik im Abendland: Von den römischen Feldmessern bis zu Descartes. Springer Verlag, Berlin 1990, ISBN 3-540-51206-3
• Günther Harmann (Hrsg.): Regiomontanus-Studien. (= Österreichische Akademie der Wissenschaften, Philosophisch-historische Klasse, Sitzungsberichte, Bd. 364; Veröffentlichungen der Kommission für Geschichte der Mathematik, Naturwissenschaften und Medizin, Heft 28-30), Wien 1980. ISBN 3-7001-0339-5
• Samuel Eliot Morison, Christopher Columbus, Mariner, Boston, Little, Brown and Company, 1955.

External links

• Adam Mosley, Regiomontanus Biography, web site at the Department of History and Philosophy of Science of the University of Cambridge (1999).
• Electronic facsimile-editions of the rare book collection at the Vienna Institute of Astronomy
• Regiomontanus and Calendar Reform
• Polybiblio: Regiomontanus, Johannes/Santbech, Daniel, ed. De Triangulis Planis et Sphaericis libri quinque. Basel Henrich Petri & Petrus Perna 1561
• Engl. Biographie bei MacTutor
• Joannes Regiomontanus: Calendarium, Venedig 1485, Digitalisat
• Beitrag bei „Astronomie in Nürnberg“
• Digitalisierte Werke von Regiomontanus - SICD der Universitäten von Strasbourg