Born: Weil der Stadt, Germany, 27 Dec. 1571
Died: Regensburg, 15 Nov. 1630
Dateinfo: Dates Certain
Common soldier of fortune.
Birth: Weil der Stadt, Germany
Death: Regensburg, Germany
Schooling: Tübingen, M.A.
1579, German and Latin Schreibschule, Leonberg.
1584, Adelberg monastery school (lower seminary).
1586, Maulbronn, a prepatory school for the university of Tuebingen
1587, matriculated Univ. of Tuebingen, but the Stift, the seminary
for scholarship students was full, so he stayed at Maulbronn for another
two years. 1589, taken into the Stift.
1588, passed Baccalaureate exam.
1591, M.A., Tuebingen. He began the theology course, but was called
away to Graz in second year.
6. Scientific Disciplines
Primary: Astronomy, Optics, Mathematics
7. Means of Support
Primary: Schoolmastering, Patronage
Secondary: Per (From Wife), Astrology, Calendars
Education: After passing competitive Wuerttemberg state examinations
he entered the school at Maulbronn. In 1589, he entered the Stift as a
scholarship student, receiving 6 gulden per year; as a scholarship student
he was forever bound into ducal service. In addition, his maternal grandfather
granted him the income from a meadow.
Graz: 1594, teacher of mathematics at the Lutheran Stiftschule at Graz.
He earned a salary of 150 gulden (his predecessor had received 200), which
was raised to 200 after his marriage, and was granted 60 gulden moving
The job of district mathematician and calendar maker was later added
to his duties. He made 5 calendars in all; for the first he received an
honorarium of 20 gulden (no information on the others).
He also received income doing astrological nativities and prognostications
1597, married the reasonably wealthy two-time widow, daughter of a
wealthy mill owner, Barbara Mueller. Her wealth was tied up in land, and
was sufficient, Kepler reckoned, to support him after a few years. Her
holdings included 10,000 gulden from which Kepler received 70 gulden for
maintenance, the yield of a vineyard, and a house.
Unfortunately, it was difficult to liquidate her assets when Kepler
was forced to leave Catholic Graz summarily in 1598, especially because
it became illegal for Protestants to lease to Catholics. He was allowed
to return, but sought other employment, working for a few months with Tycho
Brahe, but then returning shortly to Graz before being banished altogether
in 1600. Upon his ultimate expulsion, he was dismissed from his job, paid
a half-year's salary, and provided with a letter of recommendation. His
exit tax was lowered to 5% from 10%.
1600, went to work for Tycho Brahe in Prague, until Tycho died and
Kepler assumed his position.
1601, Imperial Mathematician to Rudolf (500 gulden salary).
Barbara inherited about 3000 gulden of landed property from her father
in 1603. She died in 1611, leaving no will and consequently he got nothing,
except for 2000 gulden for her children which he invested (1615) in the
treasury of the Upper Austrian representatives.
Rudolf abdicated in 1611. In 1612, he died, freeing Kepler to leave
1612-1628, district mathematician and teacher in Linz (to which was
added the task of completing a map of Upper Austria, which he later had
removed). He received a salary of 400 gulden (plus travel expenses for
the map). (In late 1616, after a political battle over whether he ought
to be retained, he was granted a small honorarium as a consolation for
1613, he married an orphan, Susanna Reuttinger, a ward of Baroness
Elizabeth von Starhemberg.
While in Linz, Kepler again supplemented his income with proceeds from
calendars. For instance, he paid for the publication of the ephemeredes
of 1617 with a calendar for 1616. In all, he made six popular calendars
between 1617 and 1624.
Kepler was allowed to stay on in Linz after the expulsion of the Protestants
in 1626, and even retained his position despite a prolonged absence from
1612, Emperor Matthais continued the post of Imperial Mathematician
at reduced salary of 300 fl/yr plus 60 gulden for dwellings and wood costs.
and gave his consent for Kepler to move to Linz.
Ferdinand continued Kepler's appointment as imperial mathematician
until Kepler's death.
1628, moved to Sagan to work for Albrecht von Wallenstein, at a salary
of 1000 gulden, and a press, for which Wallenstein promised to provide
twenty bales of paper and 1,040 gulden printing costs annually.
In 1630, the congress of electors dismissed Wallenstein. Kepler tried
to return to Linz, to collect on two 6% bonds (2000 and 1500 gulden), but
died en route.
Types: Scientist, Court Official, Aristocrat, Government Official
Education: After Landesexamen in 1583, Kepler got a scholarship from
the Duke of Wuerttemberg; this scholarship bound him forever into ducal
service. In 1590, the magistrate of Weil proposed him to the senate of
the university of Tuebingen for a stipend of 20 gulden per year, which
was granted. The senate renewed it in 1591. The senate then recommended
him for the post of teacher of mathematics to the protestant school at
Graz: For moving to Graz, Kepler received a loan of 50 gulden from
Prof. Gerlach, the superintendent of the school; Kepler was later granted
60 gulden moving expenses. The commissioners of the school upon the occasion
of his wedding granted him as a "veneration" a silver cup worth 27 gulden.
Kepler requested and received from the commissioners a raise to a 200 gulden
salary after his wedding.
He was sought out by Lords to do nativities and prognostications with
which he supplemented his income. (Include this under Miscellaneous).
The city granted him a honorarium of 20 gulden for his first calendar.
The city was generally kind to him; after the expulsion of Protestants
he was given a half-year's salary and a letter or recommendation.
In 1596, he visited the Duke of Wuerttemberg and presented him with
the idea of an artistic representation of his system of nested spheres
from the Mysterium which he wanted to dedicate to the Duke. He later applied
to Duke Johann Friedrich of Wuerttemberg for a job, but was rejected because
he was suspected of being "a sly Calvinist."
The Duke of Wuerttemberg later arranged that the court documents of
Kepler's mother's trial be sent to Tuebingen for the decision of the legal
faculty (in which Kepler had a contact, Christoph Besold), and he was responsible
for the order that she be absolved and the charges dismissed.
The Mysterium was dedicated to the estates of Styria, from whom Kepler
received a 250 gulden honararium in 1600.
After the general expulsion order for Protestant teachers in 1598,
archduke Ferdinand made an exception in the case of Kepler, allowing him
to continue as district mathematician. Kepler attributed his favor at court
to the regimental counsellor Manechio. Ferdinand also rewarded Kepler for
an astronomical essay Kepler addressed to him in 1600. After the expulsion
of all Protestants, Ferdinand ordered Kepler be reimbursed his 5% exit
tax, but this was never carried out.
As emperor, Ferdinand confirmed him as imperial mathematician, and
again excepted him when expelling non- Catholic teachers. Ferdinand also
finally wrote drafts to pay him some of his back pay to finance the publication
of the Rudolfine Tables, which was eventually dedicated to him.
Ferdinand approved Kepler's move to Ulm in 1626.
He received Kepler graciously in Prague in 1627, awarding him 4000
gulden (in drafts) for dedication of the Rudolfine Tables. He could have
stayed in service, but would have had to become Catholic.
Even as Kepler lay dying the Emperor sent a gentleman with 25 or 30
Hungarian ducats to his aid. The Emperor owed 12,694 gulden to his family
in 1633. Though claims continued to be made up until 1717, this money was
At the end of his life Kepler called himself Duke of Friedland. I do
not know why. Presumably he received the title from Wallenstein or Ferdinand
(perhaps given the title after Wallenstein's downfall?).
The Bavarian chancellor Herwart von Hohenburg was a major patron to
Kepler. They corresponded and H.v.H. lent Kepler books, which he did not
have. H.v.H. was probably partly responsible for Kepler's permission to
stay in Graz (see directly above).
Kepler appealed to Michael Maestlin often as though to a patron, for
instance asking around for a job in 1600, but Maestlin seldom was able
to oblige him.
1600, Tycho supported him in Prague. Kepler moved very much in the
orbit of Tycho, including living in the same house from the beginning of
1601. Tycho assigned Kepler the task of refuting Ursus.
1601, Kepler became Imperial mathematician to Rudolf II. He had tremendous
trouble getting paid his 500 gulden salary. At one point, the Emperor paid
400 gulden in printing costs, which Kepler spent on household expenses,
he then granted an additional 500 gulden for which he reserved the entire
edition of Astronomia nova for himself (Kepler eventually had to sell the
entire edition to the printer).
He often gave extra compensation, such as a draft for 2000 talers in
1610, on which Kepler could not collect.
Kepler dedicated numerous works to the Emperor, including the Astronomia
nova, Astronomiae pars optica, and De stella nova. He also prepared numerous
reports for the Emperor on astrological or scientific matters.
After abdicating, Rudolf asked Kepler to stay on, which he did, until
the Emperor's death.
By March 1611, he was 3000 gulden in arrears.
Casting about for another job, Kepler presented a copy of the Astronomiae
pars optica to Duke Maximilian of Bavaria. The Duke's gift to Kepler was
so small that Herwart von Hohenburg increased it out of his own pocket.
Elector Ernst of Cologne sometimes occupied days of his time at court,
and lent him a telescope.
Kepler presented him with the manuscript of Dioptrice.
Baron Johann Friedrich Hoffman von Gruenbueehel und Strechau, an imperial
advisor, housed Kepler when he first visited Prague, and later provided
Kepler with two instruments built on Tychonic designs.
Kepler dedicated his first work after leaving Prague to Peter Wok von
Rosenberg, the leader of the Utraquist faction and one of the richest and
most powerful families in Bohemia.
Kepler exchanged letters with Wenzeslaus Budowetz, a Czech aristocrat.
Kepler had allies in two court advisers: Johannes Barwitz, who helped
Kepler in his fights to get paid; and Johannes Matthaeus Wackher von Wackenfels,
to whom Kepler dedicated an essay on snowflakes.
Johannes Jessenius, a distinguished anatomist at the Univ. of Prague
and a friend of Kepler, sponsored him at his first meeting with Tycho,
and later when rector (1617) he contemplated hiring Kepler.
Kepler was a frequent guest of the imperial councilor Johannes Polz.
Johann Georg Goedelmann, the ambassador to the electorate of Saxony,
took over as godfather to Kepler's son.
Kepler was a friend of Johannes Pistorius, father confessor and adviser
to Rudolf II, to whom Kepler had to report.
He dedicated a copy of De stella novis to King James I. Kepler was
also going to dedicate the Harmonices Mundi to James I. In 1620, the English
ambassador, Sir Henry Wotton, visited him and invited him to England.
In a vain attempt to collect on the 2000 taler draft, Kepler dedicated
Eclogae Chronicae to Tobias Scultetus, an imperial advisor, who had been
appointed fiscal procurator in Silesia.
Previous to the Kepler's application to become mathematician in Linz,
he had been invited to come to Linz by Austrian Lords, such as Helmhard
Linz Patrons: Baron Erasmus von Starhemberg and Georg Erasmus von Tschernembl,
the Protestant leaders of Upper Austria; the Lords von Polheim, Maximilian
von Liechtenstein and Helmhard von Joerger.
Emperor Matthias, who succeeded Rudolf, continued Kepler's position
and paid Kepler 400 gulden for finishing the Rudolfine Tables etc.
After Magini's death Giovanni Antonio Roffeni, prof. of philosophy
at Bologna, offered Kepler the job, but he declined.
The representatives of Upper Austria were Kepler's major patrons in
Linz. There was an occasion in 1616 when Kepler became the object of a
political fight among the representatives, with the Lords facing off against
the knights and the Lords prevailing on Kepler's side (see above). The
representatives presented him with a goblet worth 40-50 gulden on the occasion
of his second marriage. Kepler presented Stereometria to the reps., who
granted him 150 gulden. The Epitome is dedicated to them as well. In 1628,
the representatives paid him 200 gulden for the presentation of the Rudolfine
Tables, paid his traveling expenses, and gave their consent to be dismissed.
Kepler dedicated the ephemerides of 1621-1629 (1630) to the representatives.
Kepler's best friend for almost twenty years was the Strasburg humanist
and noble Matthias Bernegger, to whom Kepler appealed on occasion for a
Kepler produced a belated dedication sheet for the Harmonice mundi
(1620) to Frederick V of the Palatinate, the winter-king and son-in-law
of James I, whom Kepler saw as a great hope in matters of creed.
The printing of the Epitome was subsidized by Abbot Anton von Kremsmuenster,
president of the prince's private exchequer and previous member of the
representatives of Upper Austria. He helped Kepler in his effort to use
some of the money still owed him by Rudolf to finance the publication of
the Rudolfine Tables.
The book on logarithms (1624) is dedicated to Landgrave Philip of Hesse-Butzbach,
who had it printed in Marburg. Later, when visiting the Landgrave at Butzbach,
he had been attracted by the instruments and facilities. Landgrave Philip
was willing to use his influence with Landgrave Georg to whom Kepler and
submitted a petition for interim employment (1627) and had asked to use
his influence with the Duke of Wuerttemberg. Georg offered him a house
in Marburg and support should the emperor dismiss him.
The imperial vice-chancellor, Baron Ludwig of Ulm intervened for Kepler
at one point in Kepler's attempt to get paid.
Count von Herbersdorf, president of the Bavarian district, succeeded
in getting permission for Kepler to hire printers regardless of creed after
the Protestants had been expelled from Linz.
Kepler was assisted to remove the seal of the reformation commission
on his library by the Jesuit Father Paul Guldin in Vienna (he wanted to
borrow some of the books under seal).
In Ulm (1626) Kepler had friends in Gregor Horst, previously professor
of medicine in Wittenberg and Giessen and physician- in-ordinary to Landgrave
Ludwig of Hesse, with whom he stayed; and Johann Baptist Hebenstreit, rector
of the gymnasium, who looked after the bales of paper Kepler had purchased
for the Rudolfine Tables.
Albrecht von Wallenstein, imperial General-colonel- commander-in-chief
and General of the Baltic and oceanic seas, and holder of the duchies of
Friedland and Sagan, was Kepler's last major patron. An avid believer in
astrological prognostication, he had requested an anonymous nativity from
Kepler as early as 1608 (though Kepler knew who it was), and had asked
for an update in 1624. He returned an honorarium and a promise of "princely
favors" for whenever Kepler would be in need of them. His most attractive
feature to Kepler was his belief in the peaceful co-existance of creeds,
but in 1628 all citizens of Sagan were ordered to become Catholic or leave,
though Kepler and his printers were again excepted. Kepler dedicated the
ephemerides for 1629-1639 (1630) and a short work in reply to the Jesuit
Johannes Terrentius (1630) to Wallenstein.
Philip Mueller, professor at Leipzig, with whom Kepler corresponded,
was able to get Kepler a press that he could take to Sagan.
Dr. Thomas Lindemann, rector of the University of Rostock called Kepler
to the university (1629). Before taking the job Kepler demanded that Wallenstein
get him released from imperial service and get him the 11,817 gulden he
was still owed by the Emperor (he probably didn't really want to go).
9. Technological Involvement
Types: Hydraulics, Instruments, Applied Mathematics
Kepler erected an instrument in Graz to observe a solar eclipse.
He designed a model of the nested spheres, which never got completed.
He also designed a small fountain based on a valveless pump, which he had
Joost Buergi construct and then presented to the Emperor.
Part of his duties in Linz was to be the completion of a map of Upper
Austria. I am not aware that he actually did this.
In 1613 Kepler was ordered by the Emperor to Regensburg to assist in
the debate about the reform of the calendar.
In Ulm, Kepler was asked to help in the regulation of the town's weights
and measures. He solved the problem in a lengthy essay and designed a new
regulatory measuring basin.
To his work on logarithms I add his calculation of the volume of casks.
10. Scientific Societies
He corresponded with (among others): David Fabricius, Johannes Fabricius,
Tycho Brahe, Michael Maestlin, Longomontanus [Severin], Thomas Harriot.