Alternate Names

Moestlinus; Möschlin, Michael; Möstlin, Michael

BornGöppingen, Baden-Württemberg, Germany, 30 September 1550

DiedTübingen, Baden-Württemberg, Germany, 20/30 October 1631

Michael Mästlin was a noted observer and mathematician himself but is perhaps best known as the teacher of Johannes Kepler .

Mästlin was the son of Jakob Mästlin and Dorothea Simon (died: 1565), who were pious Lutherans; he had a younger brother and an older sister. Young Michael was sent to the monastic school in Königsbronn, and eventually he enrolled at Tübingen University in 1568. There, Mästlin studied mathematics and astronomy under Philip Apian (the son of the famous astronomer Peter Apian ), whom Mästlin eventually replaced. Mästlin received his master’s degree, summa cum laude, from Tübingen University in 1571. He tutored and taught there until he was called to be a deacon at the Lutheran Church in Backnang in 1576. There, Mästlin married Margarete Grüninger (1551–1588) in April 1577, who bore him three sons and three daughters; she died (possibly due to childbirth complications), with their sixth child. Mästlin then married Margarete Burkhardt, a daughter of a Tübingen professor, in 1589; they had eight more children.

Mästlin’s publication of his careful observations of the comet of 1577 brought him fame as an astronomer. His reputation rose across Europe, leading to his appointment as a professor of mathematics at the University of Heidelberg in 1580. In 1584 Mästlin returned to the faculty at Tübingen, where he remained until his death.

For a while in the late 1570s, Mästlin was apparently the chief scientific advisor to his patron, Duke Ludwig III of Württemberg. Ludwig’s successor, Duke Friedrich I, also relied on advice and opinions from Mästlin. At Tübingen, Mästlin was elected dean of the arts faculty several times. He was well liked by both his colleagues and his students. Mästlin was very generous both to his family and to others. He was a religious man; he followed the Lutheran line in opposing the Gregorian calendar reform partly because it was initiated by the pope. Mästlin had several students who became noted mathematicians, the most famous being Kepler. Mästlin also maintained interests in Biblical chronology and geography.

Mästlin was a prolific scholar of astronomy, writing extensively and corresponding with other astronomers throughout Europe. He can be considered the first astronomer to offer an orbit of a comet (though he did not use a proper procedure), putting the comet of 1577 in a heliocentric orbit just outside the orbit of Venus; he claimed that this supported the Copernican model of heliocentrism. Mästlin was an eager mathematician, working with spherical trigonometry to convert his observations to a useful format, and followed the published works of Johann Müller (Regiomontanus), Region Ontarus, Peter Apian, and Caspar Peucer in doing this. Mästlin read scholarly books very carefully, making extensive notes in many of his own books in a neat, small handwriting. For example, he heavily annotated his personal copies of Nicolaus Copernicus ’ De revolutionibus (noting, among many other things, numerous typographical errors in cataloged star positions), Tycho Brahe ’sDe mundi aetherei on the 1577 comet (carefully assessing the positional observations), and Johann Schöner’s 1544 treatise containing observations of Müller and Bernard Walther (where Mästlin seemed quite interested in eclipse measurements).

Through Mästlin’s course on astronomy used his own textbook that followed Ptolemaic themes, this was likely due to the fact that basic astronomy (as taught at a low level at that time) did not need the technical aspects of Copernicus’s heliocentrism and Müller’s spherical trigonometry. In more advanced courses, these more technical aspects were evidently taught by Mästlin, who was widely known as a heliocentrist. That reputation had its origin in Mästlin’s tract on the 1577 comet in which he placed the comet in a Venus-like orbit about the Sun, as did Brahe in his grand book on the same comet a decade later. Both Mästlin and Brahe credited the idea for such an orbit to Abū Ma ҁ shar . Kepler credited Mästlin with having introduced him to Copernicus’ philosophy during Kepler’s student years at Tübingen (1589–1594). Kepler’s mentor wrote an appendix entailing discussion of Copernican astronomy in the younger astronomer’s first major publication, Mysterium Cosmographicum (1596, Tübingen). Mästlin maintained a long, productive correspondence with Kepler on astronomical matters. Kepler probably owed much of his own development of astronomical thought over the years to the training that he received from Mästlin.

In the late 1570s, Mästlin prepared for publication his Ephemerides novae, which were ephemerides of the planets based on Copernican theory (following the work of Erasmus Reinhold ). Mästlin duly noted that the ephemerides needed correcting because the observations upon which they were based lacked accuracy, and he stated that Copernicus’ theory is truer than older ideas. Following Regiomontanus, Peter Apian, and others from the previous 100 years, Mästlin joined his own generation of observers (including Brahe) in working carefully to obtain the best positional measurements possible of celestial objects and thereby improve the state of knowledge in astronomy.

Mästlin was known in his lifetime as a first-rate astronomical observer – his good eyesight is indicated by his drawing in 1579 of 11 stars in the Pleiades – and as an astronomer who was willing to challenge intelligently the old way of thinking about astronomy through the use of observations obtained in a more detailed and systematic fashion. In his early years, Mästlin improvised by using a thread to determine the position of transient objects (1572 supernova; comet of 1577) by checking their alignments with various stars. He impressed Brahe by finding that the supernova (B Cas) showed no parallax and must therefore be as distant as the other stars, attacking the Aristotelian position that the stellar region is unchanging. By 1577 Mästlin was using a clock to record times of observation; he was the first generation of astronomers where timekeeping was taken to be important, and times were noted often, despite the poor quality of timepieces then. Mästlin’s tracts on comets and the 1572 supernova notably parallel Brahe’s own tracts on these objects in that, unlike other typical treatises on such objects in that era, they concentrated on observations and reductions of observations while keeping astrological speculation to a bare minimum. Mästlin is also credited with being the first to publish his own finding that the unlit part of the crescent Moon glows faintly due to sunlight reflected off the Earth onto the Moon.

Though he was unable to undertake a huge observational program, such as Brahe did at Hven, Mästlin was an important influence on Brahe’s work through his correspondence. Mästlin challenged his contemporaries to improve observational data rather than to just accept what had been passed down from the ancients through medieval times. He was also familiar with constructing sundials, celestial globes, quadrants, cross-staffs, and maps – all knowledge that was likely passed on to a large degree from his professor Philip Apian at Tübingen. Within 4 years of Galileo Galilei ’s first pointing a telescope skyward, Mästlin had obtained two small telescopes which, though rather poor, showed him sunspots and the satellites of Jupiter. Mästlin remained an eager astronomical observer into his late years, making notes of his observations of the comets of 1618 and of a lunar eclipse in 1628.

Much of Mästlin’s library now resides at the Municipal Library in Schaffhausen, Switzerland.