The mathematical and technical universal genius
Jost Bürgi (1552–1632) was born in Lichtenstein in the Toggenburg region of Switzerland and was appointed to high positions at the court of Prince William IV in Kassel and at the imperial court of Rudolf II in Prague. Jost Bürgi (1552-1632), who was appointed to high positions, is a universal genius in the fields of mathematics, watchmaking, globe manufacturing and astronomy. This makes him one of the most important personalities of modern times, along with his contemporaries Johannes Kepler, Galileo Galilei and Tycho Brahe.
THE UNIVERSAL MATHEMATICAL AND TECHNICAL GENIUS
Jost Bürgi was a watchmaker, instrument maker, mathematician and astronomer all rolled into one. With great technical precision, innovative designs and novel mathematical methods, he achieved the greatest things of his time in each of these fields, combining them into a unique, high-quality process chain for the new astronomy. He not only used his mathematical methods, astronomical instruments and observational data to create highly accurate celestial globes and the first star catalogue of the modern era, but also made them available to Johannes Kepler, with whom he worked closely as the Imperial Court Clockmaker in Prague from 1603 to 1612, and to whose insights he made decisive contributions.
Jost Bürgi achieved this position, the highest in the imperial watchmaker's trade and better paid than Kepler's, after only six years of schooling and an apprenticeship as a watchmaker. He was self-taught, without studying and without mastering Latin, the scientific world language of the time. His career and further training path, which he pursued while travelling, is still largely unknown today. The first time Bürgi can be traced in the archives is when he signs a contract as court watchmaker at the court of William IV of Hesse-Kassel at the age of 27. It is highly likely that he travelled from Lichtensteig via Augsburg and Nuremberg to Kassel, where he was able to develop all his ingenious skills at the observatory from 1579 to 1603. His last career move took him to Prague in 1604, at the age of 52, where he was appointed imperial watchmaker by Rudolf II. From here, Jost Bürgi returned to his adopted country of Kassel in the middle of the Thirty Years' War, where he died a month before the celebration of his 80th birthday on 31 January 1632 and found his final resting place.
THE MATHEMATICIAN
Jost Bürgi is, together with John Napier, the co-founder of the logarithmic calculation that shaped science and technology for three centuries. He is also the author of the first European application of the differential calculus to create sine tables including the generation of table values by polynomial approximation, the sine-compliant prostaspheres, the fastest determination of several sines in the desired accuracy and the most accurate sine table of his time. Jost Bürgis' mathematical methods predate those of John Napier, Henry Briggs, Isaac Newton, Gaspard Riche de Prony and Charles Babbage, who are listed in the history books as their inventors. Without the spying of Bürgis‘ “Golden Way to Sine Determination” and its intensive use by Henry Briggs, this algebraic method would have remained unused outside Bürgis’ studio until the discovery of the Bürgi manuscript "Fundamentum Astronomiae" in 2013. So it was that, although not Bürgi's name, but his inventions unfolded worldwide and partly contributed to progress under a different name, while his name was forgotten. His contemporaries, who were well acquainted with him, compared Bürgi with Archimedes and Euclid, and two imperial mathematicians referred to him as their teacher: Nicolaus ‘Ursus’ Reimers, with whom he was close friends in Kassel, and Johannes Kepler, with whom he worked together in Prague.
ASTRONOMER
Jost Bürgi worked at the first European observatory of the modern era to be permanently established by William VIII, Landgrave of Hesse-Kassel, not only as court watchmaker and instrument manager, but also as the most important sky observer. In observation series extending over several years, he determined the positions of all types of celestial objects with unrivalled precision using the angle and time-measuring instruments he had developed himself. He then used his own mathematical methods to convert these measurements into spherical position data. Together with the astronomer Christoph Rothmann, he created the first star catalogue of the modern era, which was twice as accurate as that of Tycho Brahe. Bürgi's measurements – including numerous Mars positions – were incorporated into his instruments and probably also into Johannes Kepler's calculations of an elliptical planetary orbit. On the basis of his Earth/Sun and Moon measurement series, Jost Bürgi created a solar and lunar equation clock in Kassel as early as 1591/92, which is known for its high accuracy. He realised the deviations of the clock by means of an elliptical orbit with mechanical components. Like his employer William the Wise, Jost Bürgi also propagated the heliocentric model of the cosmos proposed by Copernicus, which was still considered heretical at the time. That is why the first three-dimensional representation of Copernicus can be seen on the side of this Renaissance clock, which is now on display in Kassel.
THE WATCHMAKER
Jost Bürgi revolutionized time measurement in 1584 by constructing the world's first observatory clock with second accuracy and its use in the first star measurement according to the horizontal method. As court watchmaker at the observatory of Landgrave Wilhelm IV in Kassel, he succeeded in reducing the then highest accuracy of a quarter-hourly clock to one-minute deviation per day. To achieve this, he developed the double cross-wound escapement and the automatic intermediate winding, which, in combination with his high-precision production of the gears, enabled him to make a quantum leap that was only surpassed with the invention of the pendulum clock eight decades later. The seconds are determined by reading a second hand, but they can also be heard, enabling one-man observation. Jost Bürgi himself called the crystal globe clock shown here, which is now on display in the "Rudolfinische Kunstkammer" in Vienna, his masterpiece. It was created between 1622 and 1627 by the already 70-year-old in his workshop at Hradcany Castle in Prague. It was commissioned by Prince Karl of Liechtenstein to thank the Habsburg Emperor Ferdinand II for admitting him to the Order of the Golden Fleece.
THE SKYGLOBES ENGINEER
During his time working as a court watchmaker in Kassel, Jost Bürgi built at least ten automated celestial globes, in addition to a terrestrial globe, into which he incorporated all of his astronomical, mathematical and technical knowledge and skills. The most perfect and accurate of his automatic 3D celestial globes is considered to be the so-called Zurich Celestial Globe, which is exhibited in the Swiss National Museum and shown here. It was made in Kassel for Emperor Rudolf II in 1594. The gilded sphere, which is only 14.2 cm in diameter and whose surface area is just about the same size as an A4 sheet of paper, features 47 artistically engraved constellations by Antonin Eisenhoit, as well as 1026 fixed star positions marked according to their luminosity. Two integrated clockworks continuously show the current starry sky and, with a sun symbol, the position of the sun around the clock. This astronomical celestial automaton is not only impressive because of its high information content, but also because of the original mechanical innovations Bürgi has used to realise its functions. In its horizontal calendar ring, for example, this celestial globe displays not only the current date and the name of the day of the week but also the changing names of the ecclesiastical Sundays and holidays, automatically taking leap years into account. The accuracy of the star position readings, using three different coordinate systems for any point in the past or future, is also second to none.