# Georg von Peuerbach

**Georg von Peuerbach** (also **Georg Aunpeckh**, **Georg Purbach**, **Peurbach**, **Purbach**, **Purbachius**, (born c. May 30, 1423 in Purbach near Linz – April 8, 1461 in Vienna) was an Austrian astronomer and mathematician who is considered to be a founder of observational and mathematical astronomy in the West. Peuerbach's best-known work, the *Theoricae novae planetarum* (1454; “*New Theories of the Planets*” ) suggesting that the planets' movement is governed by the sun, became an influential textbook of planetary theory, and by the late seventeenth century, had appeared in more than 50 Latin, Hebrew and vernacular editions and commentaries. It influenced students such as Nicolaus Copernicus (1473–1543), Galileo Galilei (1564–1642), and Johannes Kepler (1571–1630).

Peuerbach collaborated with his student and colleague Regiomontanus on a number of projects, including the observation of what came to be known as Halley's comet in 1456, and of a lunar eclipse on September 3, 1457, from a site near Vienna. At his death in 1461, he asked Regiomontanus to complete an abridgment of Ptolemy’s *Almagest*, in which he calculated tables of sines for every minute of arc for a radius of 600,000 units, and introduced the use of Hindu-Arabic numerals. He is credited with the invention of several scientific instruments, including the regula, the geometrical square. Peuerbach also served as a court astrologer for King Ladislaus V. Posthumus and, later, for Emperor Frederick III.

## Life

**Georg von Peuerbach** was born Georg Aunpeckh at Peuerbach near Linz, sometime after 1421. His standard birthdate, May 30, 1423, is derived from a sixteenth-century horoscope. About the year 1440 he received the degree of master of philosophy and the free arts, *cum insigni laude*, at the University of Vienna. His teacher in mathematics was probably Johann von Gmünden. He matriculated at the University of Vienna in 1446 and received his Bachelor of Arts in 1448.

From 1448 to 1450, he traveled in northern Italy. There, Giovanni Bianchini of Ferrara and Cardinal Nicholas of Cusa, then in Rome, became interested in the young man and induced him to lecture on astronomy at the University of Ferrara. He lectured on astronomy in Padua, but refused offers of professorships at Bologna and Padua. He returned to Vienna, received his Master of Arts in 1453, and lectured on classical Latin poetry including Virgil and Juvenal. His scientific teaching was done chiefly in private, his most famous pupil being Johann Müller of Königsberg, later known as Regiomontanus.

Peuerbach’s acquaintance with Johann Nihil, astrologer of Emperor Frederick III of Hapsburg, and his reputation as a mathematician and astronomer, led to his association with several royal courts as astrologer. Among his first patrons was the emperor’s nephew, young King Ladislaus V. Posthumus, who ruled lower Austria, Bohemia and Hungary until his early death in 1457. Subsequently he served Emperor Frederick III, who held court in Wiener Neustadt, near Vienna.

At that time, the Austrian universities were very conservative and regarded the humanities with suspicion. At the court of Emperor Frederick III, the humanist Enea Silvio Piccolomini, (later Pope Pius II) gathered a group of early German humanists who studied the classical Latin writers and lived according to the urbane style. This group included Georg von Peuerbach and his student, Johannes Regiomontanus. Peuerbach’s Latin love poems and letters were considered to be in the best Latin style. Peuerbach was instrumental in bringing about a relationship between the natural sciences and the humanities. Together with his teacher, Johannes von Gmunden, and his student and colleague, Regiomontanus (J. Müller), Peuerbach established the first School of Mathematicians at the University of Vienna and made mathematics an ancillary science of astronomy.

Peuerbach collaborated with Regiomontanus on a number of projects, including the observation of what came to be known as Halley's Comet in 1456, and of a lunar eclipse on September 3, 1457 from a site near Vienna. Peuerbach's best-known work, the *Theoricae novae planetarum* (1454; “*New Theories of the Planets*”), came from lectures which he gave to the Viennese “Citizens' School” (Bürgerschule), which Regiomontanus copied in his notebook. Peuerbach also computed an influential set of eclipse tables, *Tabulae eclipsium* (c. 1459), based on the thirteenth-century *Alphonsine Tables*, that circulated widely in manuscript before the first Viennese edition in 1514. In 1460, at the behest of Johannes Cardinal Bessarion, Peuerbach began an epitome, or abridgment, of Ptolemy's *Almagest*. Cardinal Bessarion invited him to come to Rome to study Ptolemy in the original Greek,instead of from a faulty Latin translation. Peuerbach accepted on the condition that Regiomonanus accompany him, but he died in 1461 before the journey could be undertaken. At the time of his death, Peuerbach had completed only the first six of 13 books; he asked Regiomontanus to complete the work (c. 1462), which was published in 1496 as *Epytoma…in Almagestum Ptolomei.*

The Purbach crater on the Moon is named after him.

## Thought and Works

Peuerbach is considered a founder of observational and mathematical astronomy in the West. His work helped to pave the way for the Copernican conception of the world; he created a theory of planets, calculated tables of celestial eclipses, introduced the concept of the sine into trigonometry and invented a "quadratum geometricum" for measuring heights and distances.

In *Epytoma…in Almagestum Ptolomei,* the abridgment of Ptolemy's *Almagest* which was completed by his student, Regiomontanus, he replaced chords by sines, and calculated tables of sines for every minute of arc for a radius of 600,000 units. He made his observations with very simple instruments, using an ordinary plumb-line to measure the angles of elevation of the stars. He also introduced a mathematical innovation by using Hindu-Arabic numerals in his sine tables, the first transition from the duodecimal to the decimal system. Peuerbach noted several errors in Ptolemy’s calculations, but remained a devotee of the ancient Greek mathematician.

Peuerbach worked at the Observatory of Oradea/Nagyvarad in Transylvania and established in his "*Tabula Varadiensis*" that this Transylvanian town's observatory lay on the prime meridian of Earth. He is credited with the invention of several scientific instruments, including the regula, the geometrical square. Some attribute the "Jacob's Staff" to Peuerbach but this is an error, since the Jacob's Staff is known to have been in use during the thirteenth century.^{[1]}

*Theoricae nova planetarum*

Peuerbach's best-known work, the *Theoricae novae planetarum* (1454, “New Theories of the Planets”) discussed the epicycle theory of the planets first presented by Ptolemy. Peuerbach attempted to reconcile the opposing theories of the universe, the so-called homocentric spheres of Eudoxus of Cnidus and Aristotle, with Ptolemy's epicyclic trains, with an assertion that the planets revolve in transparent but solid spheres. In spite of this erroneous notion, his suggestion that the planets' movement is governed by the sun was an early step toward the refutation of the geocentric cosmology of Ptolemy. Peuerbach said little about the planetary spheres themselves, but the illustrations in the original manuscript and in first printed edition show eccentric planetary models embedded within spherical shells, with inner and outer surfaces concentric to the earth.

The first printed edition, in 1472, was the first product of Regiomontanus’ printing press in Nuremberg. Erhard Ratdolt included it in the elementary astronomical compendia he published in Venice 1482 and 1486, which were widely imitated. By the sixteenth century it had become an influential textbook of planetary theory, displacing the widely used, anonymous thirteenth-century *Theorica planetarum communis* (the *common “Theory of the Planets*”). By the late seventeenth century, *Theoricae novae planetarum* had appeared in more than 50 Latin, Hebrew and vernacular editions and commentaries. It introduced students such as Nicolaus Copernicus (1473–1543), Galileo Galilei (1564–1642), and Johannes Kepler (1571–1630) to an updated and simplified version of Ptolemy's *Almagest* that gave a physical interpretation to its mathematical models. *Theoricæ* remained the basis of academic instruction in astronomy until Copernicus’ theories became widely accepted.

*Tabulae ecclipsium*

Among Peuerbach's early astronomical works was *Tabulae ecclipsium*, which contained tables of his eclipse calculations. These were based on the thirteenth-century *Alphonsine Tables,* and employed innovative, labor-saving organization to ease computational difficulties. It circulated widely in manuscript before its first publication in Vienna in 1514. Peuerbach later published additional tables and developed several astronomical instruments for making observations, as well as a large star globe.

## Notes

- ↑ Surveyors Historical Society Jacob’s Staff. Article penned by David G. Krehbiel, as published in The Ontario Land Surveyor, Spring 1990 (copyright POB Publishing Company, Canton, Michigan). Retrieved June 20, 2007.

## Works

Of Peuerbach’s works 20 are known; among these the most important are listed below. Peuerbach composed other treatises, most still in manuscript, devoted to elementary arithmetic, sine tables, calculating devices, and the construction of astronomical instruments (gnomons, astrolabes, and quadrants).

*Theoricæ novæ planetarum, id est septem errantium siderum nec non octavi seu firmamenti*(first ed., Nuremberg: 1472, by Regiomontanus; followed by others in Milan and Ingolstadt).*Sex primi libri epitomatis Almagesti*, completed by Regiomontanus (Venice: 1496; Basle: 1534; Nuremberg: 1550).*Tabulæ eclypsium super meridiano Viennensi*(second ed., Vienna: 1514).*Quadratum goemetricum meridiano*(Nuremberg: 1516).*Nova tabula sinus de decem minutis in decem per multas, etc.*, completed by Regiomontanus (Nuremberg: 1541).

## References

- Glick, Thomas F., Steven John Livesey, and Faith Wallis. 2005.
*Medieval science, technology, and medicine: an encyclopedia.**Routledge encyclopedias of the Middle Ages*, 11. New York: Routledge. ISBN 0415969301 ISBN 9780415969307 - Jaki, Stanley L. 1977.
*Planets and planetarians: a history of theories of the origin of planetary systems*. New York: Wiley. ISBN 0470991496 ISBN 9780470991497 - Rommel, Otto. 1947.
*Wiener Renaissance*. Klassiker der Wiener Kultur, Bd. 1. Wien: Bellaria-Verlag. - Samhaber, Friedrich. 2000.
*Die Zeitzither: Georg von Peuerbach und das helle Mittelalter.*[Raab]: Wambacher. (In German) ISBN 3853600034 ISBN 9783853600030 - Strnadt, Julius. 1868.
*Peuerbach*. Linz: [Druck von J. Wimmer].

*This article incorporates text from the public-domain *Catholic Encyclopedia* of 1913. *

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