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Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German
astronomer An astronomer is a in the field of who focuses their studies on a specific question or field outside the scope of . They observe s such as s, s, , s and – in either (by analyzing the data) or . Examples of topics or fields astronomers stud ...

astronomer
,
mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Greek: ) includes the study of such topics as numbers ( and ), formulas and related structures (), shapes and spaces in which they are contained ( ...

mathematician
,
astrologer Astrology is a pseudoscience Pseudoscience consists of statements, beliefs, or practices that claim to be both scientific and factual but are incompatible with the scientific method The scientific method is an Empirical evidenc ...

astrologer
, natural philosopher and writer on music. He is a key figure in the 17th-century
Scientific Revolution The Scientific Revolution was a series of events that marked the emergence of modern science during the early modern period, when developments in History of mathematics#Mathematics during the Scientific Revolution, mathematics, History of phys ...

Scientific Revolution
, best known for his laws of planetary motion, and his books ''
Astronomia nova ''Astronomia nova'' (English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually become ...

Astronomia nova
'', ''
Harmonice Mundi ''Harmonices Mundi''The full title is ''Ioannis Keppleri Harmonices mundi libri V'' (''The Five Books of Johannes Kepler's The Harmony of the World''). (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic ...
'', and ''
Epitome Astronomiae Copernicanae The ''Epitome Astronomiae Copernicanae'' was an astronomy book on the heliocentric system published by Johannes Kepler in the period 1618 to 1621. The first volume (books I–III) was printed in 1618, the second (book IV) in 1620, and the third ...
''. These works also provided one of the foundations for
Newton Newton most commonly refers to: * Isaac Newton (1642–1726/1727), English scientist * Newton (unit), SI unit of force named after Isaac Newton Newton may also refer to: Arts and entertainment * Newton (film), ''Newton'' (film), a 2017 Indian fil ...

Newton
's theory of
universal gravitation Newton's law of universal gravitation is usually stated as that every particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can ...
. Kepler was a mathematics teacher at a
seminary A seminary, school of theology, theological seminary, or divinity school is an educational institution for educating students (sometimes called ''seminarians'') in scripture Religious texts, also known as scripture, scriptures, holy writ, or h ...
school in
Graz Graz ( , ; sl, Gradec) is the capital city of the n state of and in Austria after . As of 1 January 2021, it had a population of 331,562 (294,236 of whom had principal-residence status). In 2018, the population of the Graz (LUZ) stood at 652 ...

Graz
, where he became an associate of
Prince Hans Ulrich von Eggenberg
Prince Hans Ulrich von Eggenberg
. Later he became an assistant to the astronomer
Tycho Brahe Tycho Brahe ( ; born Tyge Ottesen Brahe; 14 December 154624 October 1601) was a Danish , known for his accurate and comprehensive astronomical observations. He was born in , which became part of Sweden in the next century. Tycho was well known ...

Tycho Brahe
in
Prague Prague ( ; cs, Praha ; german: Prag, ; la, Praga) is the capital and largest city A city is a large human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people l ...

Prague
, and eventually the imperial mathematician to
Emperor Rudolf II Rudolf II (18 July 1552 – 20 January 1612) was Holy Roman Emperor The Holy Roman Emperor, originally and officially the Emperor of the Romans ( la, Imperator Romanorum, german: Kaiser der Römer) during the Middle Ages, and also known ...
and his two successors
MatthiasMatthias is a name derived from the Greek Ματθαίος, in origin similar to Matthew. People Notable people named Matthias include the following: In religion: * Saint Matthias Matthias (Koine Greek Koine Greek (, , Greek approximately ; ...

Matthias
and
Ferdinand II
Ferdinand II
. He also taught mathematics in
Linz Linz ( , ; cs, Linec) is the capital of Upper Austria Upper Austria (german: Oberösterreich ; bar, Obaöstareich) is one of the nine states State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly m ...
, and was an adviser to
General Wallenstein
General Wallenstein
. Additionally, he did fundamental work in the field of
optics Optics is the branch of that studies the behaviour and properties of , including its interactions with and the construction of that use or it. Optics usually describes the behaviour of , , and light. Because light is an , other forms of s ...

optics
, invented an improved version of the refracting (or Keplerian) telescope, and was mentioned in the
telescopic A telescope is an instrument designed for the observation of remote objects. Telescope(s) also may refer to: Music * The Telescopes, a British psychedelic band * Telescope (album), ''Telescope'' (album), by Circle, 2007 * The Telescope (album), '' ...

telescopic
discoveries of his contemporary
Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (; 15 February 1564 – 8 January 1642) was an Italian astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the ...

Galileo Galilei
. He was a corresponding member of the
Accademia dei Lincei The Accademia dei Lincei (; literally the "Academy An academy (Attic Greek: Ἀκαδήμεια; Koine Greek Ἀκαδημία) is an institution of secondary education, secondary or tertiary education, tertiary higher education, higher learning, ...
in Rome. Kepler lived in an era when there was no clear distinction between
astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies astronomical object, celestial objects and celestial event, phenomena. It uses mathematics, phys ...
and
astrology Astrology is a pseudoscience that claims to divination, divine information about human affairs and terrestrial events by studying the movements and relative positions of Celestial objects in astrology, celestial objects. Astrology has be ...
, but there was a strong division between astronomy (a branch of
mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities and their changes (cal ...
within the
liberal arts Liberal arts education (from Latin "free" and "art or principled practice") is the traditional academic program in Western higher education. ''Liberal arts'' takes the term ''Art (skill), art'' in the sense of a learned skill rather than spec ...
) and
physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of eve ...

physics
(a branch of
natural philosophy Natural philosophy or philosophy of nature (from ''philosophia naturalis'') was the study of and the physical that was dominant before the development of . From the ancient world, at least since , to the 19th century, ''natural philosophy' ...
). Kepler also incorporated religious arguments and reasoning into his work, motivated by the religious conviction and belief that God had created the world according to an intelligible plan that is accessible through the natural light of
reason Reason is the capacity of consciously applying logic Logic is an interdisciplinary field which studies truth and reasoning Reason is the capacity of consciously making sense of things, applying logic Logic (from Ancient Greek, Greek ...
. Kepler described his new astronomy as "celestial physics", as "an excursion into
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental quest ...

Aristotle
's ''
Metaphysics Metaphysics is the branch of philosophy that studies the first principles of being, identity and change, space and time, causality, necessity and possibility. It includes questions about the nature of consciousness and the relationship between ...
''", and as "a supplement to Aristotle's ''
On the Heavens ''On the Heavens'' (Greek: Περὶ οὐρανοῦ; Latin: ''De Caelo'' or ''De Caelo et Mundo'') is Aristotle's chief cosmological treatise: written in 350 BC it contains his astronomical theory and his ideas on the concrete workings of the ...
''", transforming the ancient tradition of physical cosmology by treating astronomy as part of a universal mathematical physics.


Early life


Childhood (1571-1590)

Kepler was born on 27 December 1571, in the
Free Imperial City In the Holy Roman Empire, the collective term free and imperial cities (german: Freie und Reichsstädte), briefly worded free imperial city (', la, urbs imperialis libera), was used from the fifteenth century to denote a self-ruling city that h ...
of
Weil der Stadt Weil der Stadt is a town of about 19,000 inhabitants in the Stuttgart Region of the German state of Baden-Württemberg Baden-Württemberg (; ) is a States of Germany, state (''Land'') in southwest Germany, east of the Rhine, which forms the s ...
(now part of the
Stuttgart Region Stuttgart Region (Baden-Württemberg Baden-Württemberg (; ), commonly shortened to BW or BaWü, is a states of Germany, German state (''Bundesland'') in Southwest Germany, east of the Rhine, which forms the southern part of Germany's western ...

Stuttgart Region
in the German state of
Baden-Württemberg Baden-Württemberg (; ) is a state (''Land'') in southwest Germany Southern Germany () as a region has no exact boundary but is generally taken to include the areas in which Upper German dialects are spoken. This corresponds roughly to the h ...
, 30 km west of Stuttgart's center). His grandfather, Sebald Kepler, had been Lord Mayor of the city. By the time Johannes was born, he had two brothers and one sister and the Kepler family fortune was in decline. His father, Heinrich Kepler, earned a precarious living as a
mercenary A mercenary, sometimes known as a soldier of fortune, is a private individual, particularly a soldier, who takes part in military conflict for personal profit, is otherwise an outsider to the conflict, and is not a member of any other official ...

mercenary
, and he left the family when Johannes was five years old. He was believed to have died in the
Eighty Years' War The Eighty Years' War ( nl, Tachtigjarige Oorlog; es, Guerra de los Ochenta Años) or Dutch War of Independence (1568–1648) was a Dutch Revolt, revolt of the Seventeen Provinces of what are today the Netherlands, Belgium and Luxembourg ag ...
in the Netherlands. His mother, Katharina Guldenmann, an innkeeper's daughter, was a healer and
herbalist Herbal medicine (also herbalism) is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine Traditional medicine (also known as indigenous or folk medicine) comprises medical aspects of tradit ...
. Born prematurely, Johannes claimed to have been weak and sickly as a child. Nevertheless, he often impressed travelers at his grandfather's inn with his phenomenal mathematical faculty. He was introduced to astronomy at an early age and developed a strong passion for it that would span his entire life. At age six, he observed the
Great Comet of 1577 The Great Comet of 1577 (official designation: C/1577 V1) is a non-periodic comet that passed close to Earth during the year 1577 AD. Having an official designation beginning with "C" classes it as a non-periodic comet, and so it is not expected t ...

Great Comet of 1577
, writing that he "was taken by
is
is
mother to a high place to look at it." In 1580, at age nine, he observed another astronomical event, a
lunar eclipse A lunar eclipse occurs when the moves into the . This can occur only when the , Earth, and Moon are exactly or very closely aligned (in ) with Earth between the other two, and only on the night of a . The type and length of a lunar eclipse dep ...

lunar eclipse
, recording that he remembered being "called outdoors" to see it and that the
moon The Moon is Earth's only natural satellite. At about one-quarter the diameter of Earth (comparable to the width of Australia (continent), Australia), it is the largest natural satellite in the Solar System relative to the size of its plane ...

moon
"appeared quite red".Koestler. ''The Sleepwalkers'', p. 234 (translated from Kepler's family horoscope). However, childhood
smallpox Smallpox was an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the infectious ...

smallpox
left him with weak vision and crippled hands, limiting his ability in the observational aspects of astronomy. In 1589, after moving through grammar school,
Latin school The Latin school was the grammar school of 14th- to 19th-century Europe, though the latter term was much more common in England. Emphasis was placed, as the name indicates, on learning to use Latin Latin (, or , ) is a classical language bel ...
, and seminary at Maulbronn, Kepler attended
Tübinger Stift The Tübinger Stift () is a hall of residence and teaching; it is owned and supported by the Evangelical-Lutheran Church in Württemberg, and located in the university city of Tübingen Tübingen (, , Swabian: ''Dibenga'') is a traditional un ...
at the
University of Tübingen The University of Tübingen, officially the Eberhard Karl University of Tübingen (german: Eberhard Karls Universität Tübingen; la, Universitas Eberhardina Carolina), is a public university, public research university located in the city of Tüb ...
. There, he studied philosophy under Vitus Müller and
theology Theology is the systematic study of the nature of the divine Divinity or the divine are things that are either related to, devoted to, or proceeding from a deity A deity or god is a supernatural The supernatural encompasses supposed ...
under Jacob Heerbrand (a student of
Philipp Melanchthon Philip Melanchthon. (born Philipp Schwartzerdt; 16 February 1497 – 19 April 1560) was a German Lutheran Lutheranism is one of the largest branches of Protestantism Protestantism is a form of Christianity Christianity is an Abraham ...
at Wittenberg), who also taught
Michael Maestlin Michael Maestlin (also Mästlin, Möstlin, or Moestlin) (30 September 1550 – 26 October 1631) was a German astronomer and mathematician, known for being the mentor of Johannes Kepler. He was a student of Philipp Apian and was known as the te ...

Michael Maestlin
while he was a student, until he became Chancellor at Tübingen in 1590.Barker, Peter; Goldstein, Bernard R. "Theological Foundations of Kepler's Astronomy", Osiris, 2nd Series, Vol. 16, Science'' in Theistic Contexts: Cognitive Dimensions'' (2001), p. 96. He proved himself to be a superb mathematician and earned a reputation as a skilful astrologer, casting
horoscope A horoscope (or other commonly used names for the horoscope in English include natal chart, astrological chart, astro-chart, celestial map, sky-map, star-chart, cosmogram, vitasphere, radical chart, radix, chart wheel or simply chart) is an ast ...
s for fellow students. Under the instruction of Michael Maestlin, Tübingen's professor of mathematics from 1583 to 1631, he learned both the
Ptolemaic system In astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies astronomical object, celestial objects and celestial event, phenomena. It uses ma ...

Ptolemaic system
and the of planetary motion. He became a at that time. In a student disputation, he defended
heliocentrism Heliocentrism is the astronomical model in which the Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's surface is land consisting of continent A continent ...
from both a theoretical and theological perspective, maintaining that the
Sun The Sun is the star A star is an astronomical object consisting of a luminous spheroid of plasma (physics), plasma held together by its own gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many othe ...

Sun
was the principal source of motive power in the universe. Despite his desire to become a minister, near the end of his studies, Kepler was recommended for a position as teacher of mathematics and astronomy at the Protestant school in Graz. He accepted the position in April 1594, at the age of 22.


Graz (1594–1600)

Before concluding his studies at Tübingen, Kepler accepted an offer to teach mathematics as a replacement to Georg Stadius at the Protestant school in Graz (now in Styria, Austria). During this period (1594–1600), he issued many official calendars and prognostications that enhanced his reputation as an astrologer. Although Kepler had mixed feelings about astrology, he believed deeply in a connection between the cosmos and the individual. He eventually published some of the ideas he had entertained while a student in the ''Mysterium Cosmographicum'' (1596), published a little over a year after his arrival at Graz. In December 1595, Kepler was introduced to Barbara Müller, a 23-year-old widow (twice over) with a young daughter, Regina Lorenz, and he began courting her. Müller, an heiress to the estates of her late husbands, was also the daughter of a successful mill owner. Her father Jobst initially opposed a marriage. Even though Kepler had inherited his grandfather's nobility, Kepler's poverty made him an unacceptable match. Jobst relented after Kepler completed work on ''Mysterium'', but the engagement nearly fell apart while Kepler was away tending to the details of publication. However, Protestant officials—who had helped set up the match—pressured the Müllers to honor their agreement. Barbara and Johannes were married on 27 April 1597. In the first years of their marriage, the Keplers had two children (Heinrich and Susanna), both of whom died in infancy. In 1602, they had a daughter (Susanna); in 1604, a son (Friedrich); and in 1607, another son (Ludwig).


Other research

Following the publication of ''Mysterium'' and with the blessing of the Graz school inspectors, Kepler began an ambitious program to extend and elaborate his work. He planned four additional books: one on the stationary aspects of the universe (the Sun and the fixed stars); one on the planets and their motions; one on the physical nature of planets and the formation of geographical features (focused especially on Earth); and one on the effects of the heavens on the Earth, to include atmospheric optics, meteorology, and astrology. He also sought the opinions of many of the astronomers to whom he had sent ''Mysterium'', among them
Reimarus Ursus Nicolaus Reimers Baer (2 February 1551 – 16 October 1600), also ''Reimarus Ursus'', ''Nicolaus Reimers Bär'' or ''Nicolaus Reymers Baer'', was an astronomer and imperial mathematician to Emperor Rudolf II. Due to his family's background, h ...
(Nicolaus Reimers Bär)—the imperial mathematician to
Rudolf II Rudolf II (18 July 1552 – 20 January 1612) was (1576–1612), and (as Rudolf I, 1572–1608), (1575–1608/1611) and (1576–1608). He was a member of the . Rudolf's legacy has traditionally been viewed in three ways:Hotson, 1999. a ...
and a bitter rival of
Tycho Brahe Tycho Brahe ( ; born Tyge Ottesen Brahe; 14 December 154624 October 1601) was a Danish , known for his accurate and comprehensive astronomical observations. He was born in , which became part of Sweden in the next century. Tycho was well known ...

Tycho Brahe
. Ursus did not reply directly, but republished Kepler's flattering letter to pursue his priority dispute over (what is now called) the
Tychonic system File:Tychonian system.svg, The Tychonic system shown in colour, with the objects that rotate around the Earth shown on blue orbits, and the objects that rotate around the Sun shown on orange orbits. Around all is a sphere of fixed stars, stars, wh ...
with Tycho. Despite this black mark, Tycho also began corresponding with Kepler, starting with a harsh but legitimate critique of Kepler's system; among a host of objections, Tycho took issue with the use of inaccurate numerical data taken from Copernicus. Through their letters, Tycho and Kepler discussed a broad range of astronomical problems, dwelling on lunar phenomena and Copernican theory (particularly its theological viability). But without the significantly more accurate data of Tycho's observatory, Kepler had no way to address many of these issues. Instead, he turned his attention to
chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronology Chronology (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European language ...
and "harmony," the
numerological Numerology is any belief in the divine or mysticism, mystical relationship between a number and one or more Coincidence#Interpretation, coinciding events. It is also the study of the numerical value of the letters in words, names, and ideas. I ...
relationships among music,
mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities and their changes (cal ...
and the physical world, and their
astrological Astrology is a pseudoscience Pseudoscience consists of statements, beliefs, or practices that claim to be both scientific and factual but are incompatible with the scientific method The scientific method is an Empirical evidenc ...
consequences. By assuming the Earth to possess a soul (a property he would later invoke to explain how the sun causes the motion of planets), he established a speculative system connecting
astrological aspects In astrology, an aspect is an angle the Planets in astrology, planets make to each other in the horoscope, also to the ascendant, midheaven, descendant (astrology), descendant, Imum coeli, lower midheaven, and other points of astrological interest ...
and astronomical distances to
weather Weather is the state of the atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a p ...
and other earthly phenomena. By 1599, however, he again felt his work limited by the inaccuracy of available data—just as growing religious tension was also threatening his continued employment in Graz. In December of that year, Tycho invited Kepler to visit him in
Prague Prague ( ; cs, Praha ; german: Prag, ; la, Praga) is the capital and largest city A city is a large human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people l ...

Prague
; on 1 January 1600 (before he even received the invitation), Kepler set off in the hopes that Tycho's patronage could solve his philosophical problems as well as his social and financial ones.


Scientific career


Prague (1600–1612)

On 4 February 1600, Kepler met
Tycho Brahe Tycho Brahe ( ; born Tyge Ottesen Brahe; 14 December 154624 October 1601) was a Danish , known for his accurate and comprehensive astronomical observations. He was born in , which became part of Sweden in the next century. Tycho was well known ...

Tycho Brahe
and his assistants Franz Tengnagel and Longomontanus at Benátky nad Jizerou (35 km from Prague), the site where Tycho's new observatory was being constructed. Over the next two months, he stayed as a guest, analyzing some of Tycho's observations of Mars; Tycho guarded his data closely, but was impressed by Kepler's theoretical ideas and soon allowed him more access. Kepler planned to test his theory from ''Mysterium Cosmographicum'' based on the Mars data, but he estimated that the work would take up to two years (since he was not allowed to simply copy the data for his own use). With the help of Johannes Jessenius, Kepler attempted to negotiate a more formal employment arrangement with Tycho, but negotiations broke down in an angry argument and Kepler left for Prague on 6 April. Kepler and Tycho soon reconciled and eventually reached an agreement on salary and living arrangements, and in June, Kepler returned home to Graz to collect his family. Political and religious difficulties in Graz dashed his hopes of returning immediately to Brahe; in hopes of continuing his astronomical studies, Kepler sought an appointment as a mathematician to . To that end, Kepler composed an essay—dedicated to Ferdinand—in which he proposed a force-based theory of lunar motion: "In Terra inest virtus, quae Lunam ciet" ("There is a force in the earth which causes the moon to move"). Though the essay did not earn him a place in Ferdinand's court, it did detail a new method for measuring lunar eclipses, which he applied during 10 July eclipse in Graz. These observations formed the basis of his explorations of the laws of optics that would culminate in ''Astronomiae Pars Optica''. On 2 August 1600, after refusing to convert to Catholicism, Kepler and his family were banished from Graz. Several months later, Kepler returned, now with the rest of his household, to Prague. Through most of 1601, he was supported directly by Tycho, who assigned him to analyzing planetary observations and writing a tract against Tycho's (by then deceased) rival, Ursus. In September, Tycho secured him a commission as a collaborator on the new project he had proposed to the emperor: the ''
Rudolphine Tables The ''Rudolphine Tables'' ( la, Tabulae Rudolphinae) consist of a star catalogue and planetary tables published by Johannes Kepler in 1627, using observational data collected by Tycho Brahe (1546–1601). The tables are named in memory of Rudolf ...

Rudolphine Tables
'' that should replace the '''' of
Erasmus Reinhold Erasmus Reinhold (22 October 1511 – 19 February 1553) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of German ...
. Two days after Tycho's unexpected death on 24 October 1601, Kepler was appointed his successor as the imperial mathematician with the responsibility to complete his unfinished work. The next 11 years as imperial mathematician would be the most productive of his life.


Imperial Advisor

Kepler's primary obligation as imperial mathematician was to provide astrological advice to the emperor. Though Kepler took a dim view of the attempts of contemporary astrologers to precisely predict the future or divine specific events, he had been casting well-received detailed horoscopes for friends, family, and patrons since his time as a student in Tübingen. In addition to horoscopes for allies and foreign leaders, the emperor sought Kepler's advice in times of political trouble. Rudolf was actively interested in the work of many of his court scholars (including numerous
alchemists File:Aurora consurgens zurich 044 f-21v-44 dragon-pot.jpg, Depiction of Ouroboros from the alchemical treatise ''Aurora consurgens'' (15th century), Zentralbibliothek Zürich, Switzerland Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Gree ...
) and kept up with Kepler's work in physical astronomy as well. Officially, the only acceptable religious doctrines in Prague were Catholic and
Utraquist Utraquism (from the ''sub utraque specie'', meaning "under both kinds") or Calixtinism (from ; : ''calix'', mug, borrowed from Greek ''kalyx'', shell, husk; : kališníci) was a belief amongst , a reformist movement, that (both bread and wine, ...
, but Kepler's position in the imperial court allowed him to practice his Lutheran faith unhindered. The emperor nominally provided an ample income for his family, but the difficulties of the over-extended imperial treasury meant that actually getting hold of enough money to meet financial obligations was a continual struggle. Partly because of financial troubles, his life at home with Barbara was unpleasant, marred with bickering and bouts of sickness. Court life, however, brought Kepler into contact with other prominent scholars ( Johannes Matthäus Wackher von Wackhenfels,
Jost Bürgi Jost Bürgi (also ''Joost, Jobst''; Latinized surname ''Burgius'' or ''Byrgius''; 28 February 1552 – 31 January 1632), active primarily at the courts in Kassel Kassel (; in Germany, spelled Cassel until 1926) is a city on the Fulda River in ...
,
David FabriciusDavid Fabricius (9 March 1564 – 7 May 1617) was a German pastor who made two major discoveries in the early days of telescopic astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the ...
, Martin Bachazek, and Johannes Brengger, among others) and astronomical work proceeded rapidly.


Supernova of 1604

In October 1604, a bright new evening star (
SN 1604 SN 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a Type Ia supernova A type Ia supernova (read: "type one-A") is a type of supernova (bright spot on the lower left), a type Ia supernova within its host galax ...
) appeared, but Kepler did not believe the rumors until he saw it himself. Kepler began systematically observing the supernova. Astrologically, the end of 1603 marked the beginning of a fiery trigon, the start of the about 800-year cycle of s; astrologers associated the two previous such periods with the rise of
Charlemagne Charlemagne ( , ) or Charles the Great ( la, Carolus Magnus; 2 April 748 – 28 January 814) was King of the Franks The Franks—Germanic-speaking peoples that invaded the Western Roman Empire in the 5th century—were first led by i ...

Charlemagne
(c. 800 years earlier) and the birth of Christ (c. 1600 years earlier), and thus expected events of great portent, especially regarding the emperor. It was in this context, as the imperial mathematician and astrologer to the emperor, that Kepler described the new star two years later in his '' De Stella Nova''. In it, Kepler addressed the star's astronomical properties while taking a skeptical approach to the many astrological interpretations then circulating. He noted its fading luminosity, speculated about its origin, and used the lack of observed parallax to argue that it was in the sphere of fixed stars, further undermining the doctrine of the immutability of the heavens (the idea accepted since Aristotle that the
celestial spheres The celestial spheres, or celestial orbs, were the fundamental entities of the cosmology, cosmological models developed by Plato, Eudoxus of Cnidus, Eudoxus, Aristotle, Ptolemy, Copernicus, and others. In these celestial models, the diurnal m ...
were perfect and unchanging). The birth of a new star implied the variability of the heavens. Kepler also attached an appendix where he discussed the recent chronology work of the Polish historian Laurentius Suslyga; he calculated that, if Suslyga was correct that accepted timelines were four years behind, then the
Star of Bethlehem The Star of Bethlehem, or Christmas Star, appears in the nativity of Jesus, nativity story of the Gospel of Matthew where "wise men from the East" (biblical Magi, Magi) are inspired by the star to travel to Jerusalem. There, they meet King Herod ...

Star of Bethlehem
—analogous to the present new star—would have coincided with the first great conjunction of the earlier 800-year cycle. Over the following years, Kepler attempted (unsuccessfully) to begin a collaboration with Italian astronomer
Giovanni Antonio Magini Giovanni Antonio Magini (in Latin, Maginus) (13 June 1555 – 11 February 1617) was an Italy, Italian astronomer, astrologer, cartographer, and mathematician. His Life He was born in Padua, and completed studies in philosophy in Bologna in 157 ...
, and dealt with chronology, especially the dating of events in the life of Jesus. Around 1611, Kepler circulated a manuscript of what would eventually be published (posthumously) as '' Somnium'' he Dream Part of the purpose of ''Somnium'' was to describe what practicing astronomy would be like from the perspective of another planet, to show the feasibility of a non-geocentric system. The manuscript, which disappeared after changing hands several times, described a fantastic trip to the Moon; it was part allegory, part autobiography, and part treatise on interplanetary travel (and is sometimes described as the first work of science fiction). Years later, a distorted version of the story may have instigated the witchcraft trial against his mother, as the mother of the narrator consults a demon to learn the means of space travel. Following her eventual acquittal, Kepler composed 223 footnotes to the story—several times longer than the actual text—which explained the allegorical aspects as well as the considerable scientific content (particularly regarding lunar geography) hidden within the text.


Later life


Troubles

In 1611, the growing political-religious tension in Prague came to a head. Emperor Rudolf — whose health was failing—was forced to abdicate as
King of Bohemia of the King of the Romans King of the Romans ( la, Rex Romanorum; german: König der Römer) was the title used by the German king following his election An election is a formal group decision-making process by which a population choo ...
by his brother
MatthiasMatthias is a name derived from the Greek Ματθαίος, in origin similar to Matthew. People Notable people named Matthias include the following: In religion: * Saint Matthias Matthias (Koine Greek Koine Greek (, , Greek approximately ; ...

Matthias
. Both sides sought Kepler's astrological advice, an opportunity he used to deliver conciliatory political advice (with little reference to the stars, except in general statements to discourage drastic action). However, it was clear that Kepler's future prospects in the court of Matthias were dim. Also in that year, Barbara Kepler contracted Hungarian spotted fever, then began having
seizure An epileptic seizure, formally known as a seizure, is a period of symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower tem ...
s. As Barbara was recovering, Kepler's three children all fell sick with smallpox; Friedrich, 6, died. Following his son's death, Kepler sent letters to potential patrons in
Württemberg Württemberg ( ; ) is a historical German territory roughly corresponding to the cultural and linguistic region of Swabia upThe coat of arms of Baden-Württemberg shows the three lions passant of the arms of the Duchy of Swabia, in origin th ...
and
Padua Padua ( ; it, Padova ; vec, Pàdova) is a city and ''comune The (; plural: ) is a Administrative division, local administrative division of Italy, roughly equivalent to a township or municipality. Importance and function The pro ...
. At the
University of Tübingen The University of Tübingen, officially the Eberhard Karl University of Tübingen (german: Eberhard Karls Universität Tübingen; la, Universitas Eberhardina Carolina), is a public university, public research university located in the city of Tüb ...
in Württemberg, concerns over Kepler's perceived
Calvinist Calvinism (also called the Reformed tradition, Reformed Christianity, Reformed Protestantism, or the Reformed faith) is a major branch of Protestantism Protestantism is a form of Christianity Christianity is an , based on the a ...
heresies in violation of the
Augsburg Confession The Augsburg Confession, also known as the Augustan Confession or the Augustana from its Latin name, ''Confessio Augustana'', is the primary confession of faith of the Lutheran Church and one of the most important documents of the Protestant Reform ...
and the
Formula of Concord Formula of Concord (1577) (German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * ...
prevented his return. The
University of Padua The University of Padua ( it, Università degli Studi di Padova, UNIPD) is an Italian university located in the city of Padua, region of Veneto it, Veneto (man) it, Veneta (woman) , population_note = , population_blank1_title = , p ...
—on the recommendation of the departing Galileo—sought Kepler to fill the mathematics professorship, but Kepler, preferring to keep his family in German territory, instead travelled to Austria to arrange a position as teacher and district mathematician in
Linz Linz ( , ; cs, Linec) is the capital of Upper Austria Upper Austria (german: Oberösterreich ; bar, Obaöstareich) is one of the nine states State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly m ...
. However, Barbara relapsed into illness and died shortly after Kepler's return. Kepler postponed the move to Linz and remained in Prague until Rudolf's death in early 1612, though between political upheaval, religious tension, and family tragedy (along with the legal dispute over his wife's estate), Kepler could do no research. Instead, he pieced together a chronology manuscript, ''Eclogae Chronicae'', from correspondence and earlier work. Upon succession as Holy Roman Emperor, Matthias re-affirmed Kepler's position (and salary) as imperial mathematician but allowed him to move to Linz.


Linz (1612-1620)

In Linz, Kepler's primary responsibilities (beyond completing the ''Rudolphine Tables'') were teaching at the district school and providing astrological and astronomical services. In his first years there, he enjoyed financial security and religious freedom relative to his life in Prague—though he was excluded from
Eucharist The Eucharist (; grc-gre, εὐχαριστία, eucharistía, thanksgiving) also known as Holy Communion and the Lord's Supper, among other names, is a Christian Christians () are people who follow or adhere to Christianity, a monothe ...

Eucharist
by his Lutheran church over his theological scruples. It was also during his time in Linz that Kepler had to deal with the accusation and ultimate verdict of witchcraft against his mother
Katharina Katharina is a feminine given name. It is a German form of Katherine Katherine, Catherine, and other variations are feminine names A name is a term used for identification by an external observer. They can identify a class or category of th ...
in the Protestant town of
Leonberg Leonberg is a town in the Germany, German federal state of Baden-Württemberg about to the west of Stuttgart, the state capital. About 45,000 people live in Leonberg, making it the third-largest borough in the Landkreis, rural district (''Landk ...

Leonberg
. That blow, happening only a few years after Kepler's
excommunication Excommunication is an institutional act of religious censure A censure is an expression of strong disapproval or harsh criticism. In parliamentary procedure, it is a debatable main motion that could be adopted by a majority vote. Among the ...

excommunication
, is not seen as a coincidence but as a symptom of the full-fledged assault waged by the Lutherans against Kepler. His first publication in Linz was ''De vero Anno'' (1613), an expanded treatise on the year of Christ's birth. He also participated in deliberations on whether to introduce 's reformed calendar to Protestant German lands. On 30 October 1613, Kepler married the 24-year-old Susanna Reuttinger. Following the death of his first wife Barbara, Kepler had considered 11 different matches over two years (a decision process formalized later as the marriage problem). He eventually returned to Reuttinger (the fifth match) who, he wrote, "won me over with love, humble loyalty, economy of household, diligence, and the love she gave the stepchildren." The first three children of this marriage (Margareta Regina, Katharina, and Sebald) died in childhood. Three more survived into adulthood: Cordula (born 1621); Fridmar (born 1623); and Hildebert (born 1625). According to Kepler's biographers, this was a much happier marriage than his first. On 8 October 1630, Kepler set out for Regensburg, hoping to collect interest on work he had done previously. A few days after reaching Regensburg, Kepler became sick, and progressively became worse. On 15 November 1630, just over a month after his arrival, he died. He was buried in a Protestant churchyard that was completely destroyed during the
Thirty Years' War The Thirty Years' War was a conflict fought largely within the Holy Roman Empire The Holy Roman Empire ( la, Sacrum Romanum Imperium; german: Heiliges Römisches Reich) was a multi-ethnic complex of territories in Western Europe, Weste ...
.


Christianity

Kepler's belief that God created the cosmos in an orderly fashion caused him to attempt to determine and comprehend the laws that govern the natural world, most profoundly in astronomy. The phrase "I am merely thinking God's thoughts after Him" has been attributed to him, although this is probably a capsulized version of a writing from his hand:
Those laws f natureare within the grasp of the human mind; God wanted us to recognize them by creating us after his own image so that we could share in his own thoughts.


Astronomy


''Mysterium Cosmographicum''

Kepler's first major astronomical work, '' Mysterium Cosmographicum'' (''The Cosmographic Mystery'', 1596), was the first published defense of the Copernican system. Kepler claimed to have had an
epiphany Epiphany may refer to: * Epiphany (feeling), an experience of sudden and striking insight Religion * Epiphany (holiday), a Christian holiday celebrating the revelation of God the Son as a human being in Jesus Christ ** Epiphany season, or Epiphan ...
on 19 July 1595, while teaching in
Graz Graz ( , ; sl, Gradec) is the capital city of the n state of and in Austria after . As of 1 January 2021, it had a population of 331,562 (294,236 of whom had principal-residence status). In 2018, the population of the Graz (LUZ) stood at 652 ...

Graz
, demonstrating the periodic
conjunction Conjunction may refer to: * Conjunction (astronomy), in which two astronomical bodies appear close together in the sky * Conjunction (astrology), astrological aspect in horoscopic astrology * Conjunction (grammar), a part of speech * Logical conjun ...
of
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It only has one-eighth the average density of Earth; how ...

Saturn
and
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

Jupiter
in the
zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic The ecliptic is the plane (geometry), plane of Earth's orbit around the Sun. From the perspecti ...

zodiac
: he realized that
regular polygon In , a regular polygon is a that is (all angles are equal in measure) and (all sides have the same length). Regular polygons may be either or . In the , a sequence of regular polygons with an increasing number of sides approximates a , if the ...
s bound one inscribed and one circumscribed circle at definite ratios, which, he reasoned, might be the geometrical basis of the universe. After failing to find a unique arrangement of polygons that fit known astronomical observations (even with extra planets added to the system), Kepler began experimenting with 3-dimensional
polyhedra In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position o ...
. He found that each of the five
Platonic solid In three-dimensional space, a Platonic solid is a Regular polyhedron, regular, Convex set, convex polyhedron. It is constructed by Congruence (geometry), congruent (identical in shape and size), regular polygon, regular (all angles equal and all sid ...
s could be inscribed and circumscribed by spherical orbs; nesting these solids, each encased in a sphere, within one another would produce six layers, corresponding to the six known planets—
Mercury Mercury usually refers to: * Mercury (planet) Mercury is the smallest planet in the Solar System and the closest to the Sun. Its orbit around the Sun takes 87.97 Earth days, the shortest of all the Sun's planets. It is named after the Roman g ...

Mercury
,
Venus Venus is the second planet from the Sun. It is named after the Venus (mythology), Roman goddess of love and beauty. As List of brightest natural objects in the sky, the brightest natural object in Earth's night sky after the Moon, Venus can ...

Venus
,
Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

Earth
,
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury (planet), Mercury. In English, Mars carries the name of the Mars (mythology), Roman god of war and is often referred to ...

Mars
, Jupiter, and Saturn. By ordering the solids selectively—
octahedron In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces, twelve edges, and six vertices. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral tri ...

octahedron
,
icosahedron In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non-similarity (geometry), similar shapes of icosahedra, some of them ...

icosahedron
,
dodecahedron In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position o ...

dodecahedron
,
tetrahedron In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position ...

tetrahedron
,
cube In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position ...

cube
—Kepler found that the spheres could be placed at intervals corresponding to the relative sizes of each planet's path, assuming the planets circle the Sun. Kepler also found a formula relating the size of each planet's orb to the length of its
orbital period The orbital period is the time a given astronomical object takes to complete one orbit around another object, and applies in astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of th ...
: from inner to outer planets, the ratio of increase in orbital period is twice the difference in orb radius. However, Kepler later rejected this formula, because it was not precise enough. Kepler thought the ''Mysterium'' had revealed God's geometrical plan for the universe. Much of Kepler's enthusiasm for the Copernican system stemmed from his
theological Theology is the systematic study of the nature of the divine and, more broadly, of religious belief. It is taught as an academic discipline An academic discipline or academic field is a subdivision of knowledge Knowledge is a familiarity ...
convictions about the connection between the physical and the ; the universe itself was an image of God, with the Sun corresponding to the Father, the stellar sphere to the
Son A son is a male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot sexual reproduction ...

Son
, and the intervening space between them to the
Holy Spirit In Abrahamic religions, the Holy Spirit is an aspect or agent of God in Abrahamic religions, God, by means of which God communicates with people or acts on them. In Judaism, it refers to the divine force, quality, and influence of God over the ...

Holy Spirit
. His first manuscript of ''Mysterium'' contained an extensive chapter reconciling heliocentrism with biblical passages that seemed to support geocentrism. With the support of his mentor Michael Maestlin, Kepler received permission from the Tübingen university senate to publish his manuscript, pending removal of the Bible
exegesis Exegesis (; from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is app ...
and the addition of a simpler, more understandable, description of the Copernican system as well as Kepler's new ideas. ''Mysterium'' was published late in 1596, and Kepler received his copies and began sending them to prominent astronomers and patrons early in 1597; it was not widely read, but it established Kepler's reputation as a highly skilled astronomer. The effusive dedication, to powerful patrons as well as to the men who controlled his position in Graz, also provided a crucial doorway into the . In 1621, Kepler published an expanded second edition of ''Mysterium'', half as long again as the first, detailing in footnotes the corrections and improvements he had achieved in the 25 years since its first publication. In terms of impact, the ''Mysterium'' can be seen as an important first step in modernizing the theory proposed by
Copernicus Nicolaus Copernicus (; pl, Mikołaj Kopernik; gml, link=no, Niclas Koppernigk, modern: ''Nikolaus Kopernikus''; 19 February 1473 – 24 May 1543) was a Renaissance polymath, active as a mathematician, astronomer, and Catholic Church, C ...

Copernicus
in his ''
De revolutionibus orbium coelestium ''De revolutionibus orbium coelestium'' (; English translation: ''On the Revolutions of the Heavenly Spheres'') is the seminal work on the heliocentric theory Heliocentrism is the astronomical model in which the Earth Earth is the third ...

De revolutionibus orbium coelestium
''. Whilst Copernicus sought to advance a heliocentric system in this book, he resorted to Ptolemaic devices (viz., epicycles and eccentric circles) in order to explain the change in planets' orbital speed, and also continued to use as a point of reference the center of the Earth's orbit rather than that of the Sun "as an aid to calculation and in order not to confuse the reader by diverging too much from Ptolemy." Modern astronomy owes much to ''Mysterium Cosmographicum'', despite flaws in its main thesis, "since it represents the first step in cleansing the Copernican system of the remnants of the Ptolemaic theory still clinging to it."


''Astronomia Nova''

The extended line of research that culminated in ''
Astronomia Nova ''Astronomia nova'' (English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually becom ...

Astronomia Nova
'' (''A New Astronomy'')—including the first two laws of planetary motion—began with the analysis, under Tycho's direction, of Mars' orbit. Kepler calculated and recalculated various approximations of Mars' orbit using an
equant Image:Ptolemaic elements.svg, 250px, The basic elements of Ptolemaic astronomy, showing a planet on an epicycle (smaller dashed circle), a deferent (larger dashed circle), the eccentric (×) and an equant (•). Equant (or punctum aequans) is a mat ...

equant
(the mathematical tool that Copernicus had eliminated with his system), eventually creating a model that generally agreed with Tycho's observations to within two
arcminute A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol ', is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The n ...
s (the average measurement error). But he was not satisfied with the complex and still slightly inaccurate result; at certain points the model differed from the data by up to eight arcminutes. The wide array of traditional mathematical astronomy methods having failed him, Kepler set about trying to fit an
ovoid An oval (from Latin ''ovum'', "egg") is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas ( projective geometry, technical drawing, etc.) it is given a more precise definition, wh ...

ovoid
orbit to the data. In Kepler's religious view of the cosmos, the Sun (a symbol of
God the Father God the Father is a title given to God In monotheism, monotheistic thought, God is conceived of as the supreme being, creator deity, creator, and principal object of Faith#Religious views, faith.Richard Swinburne, Swinburne, R.G. "God" ...

God the Father
) was the source of motive force in the Solar System. As a physical basis, Kepler drew by analogy on William Gilbert's theory of the magnetic soul of the Earth from ''
De Magnete Title page of 1628 edition ''De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure'' (''On the Magnet and Magnetic Bodies, and on That Great Magnet the Earth'') is a scientific work published in 1600 by the English physician and scien ...
'' (1600) and on his own work on optics. Kepler supposed that the motive power (or motive ''species'') radiated by the Sun weakens with distance, causing faster or slower motion as planets move closer or farther from it. Perhaps this assumption entailed a mathematical relationship that would restore astronomical order. Based on measurements of the
aphelion upright=1.15, The two-body system of interacting primary body A primary (also called a gravitational primary, primary body, or central body) is the main physical body of a gravity, gravitationally bound, multi-object system. This object consti ...

aphelion
and
perihelion upright=1.15, The two-body system of interacting primary body (yellow); both are in elliptic orbits around their center of mass">common center of mass (or barycenter), (red +). ∗Periapsis and apoapsis as distances: The smallest and largest ...

perihelion
of the Earth and Mars, he created a formula in which a planet's rate of motion is inversely proportional to its distance from the Sun. Verifying this relationship throughout the orbital cycle required very extensive calculation; to simplify this task, by late 1602 Kepler reformulated the proportion in terms of geometry: ''planets sweep out equal areas in equal times''—his second law of planetary motion. He then set about calculating the entire orbit of Mars, using the geometrical rate law and assuming an egg-shaped
ovoid An oval (from Latin ''ovum'', "egg") is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas ( projective geometry, technical drawing, etc.) it is given a more precise definition, wh ...
orbit. After approximately 40 failed attempts, in late 1604 he at last hit upon the idea of an ellipse, which he had previously assumed to be too simple a solution for earlier astronomers to have overlooked. Finding that an elliptical orbit fit the Mars data, Kepler immediately concluded that ''all planets move in ellipses, with the Sun at one focus''—his first law of planetary motion. Because he employed no calculating assistants, he did not extend the mathematical analysis beyond Mars. By the end of the year, he completed the manuscript for ''Astronomia nova'', though it would not be published until 1609 due to legal disputes over the use of Tycho's observations, the property of his heirs.


''Epitome of Copernican Astronomy''

Since completing the ''Astronomia Nova'', Kepler had intended to compose an astronomy textbook that would cover all the fundamentals of heliocentric astronomy. Kepler spent the next several years working on what would become ''Epitome Astronomiae Copernicanae'' (''Epitome of Copernican Astronomy''). Despite its title, which merely hints at heliocentrism, the ''Epitome'' is less about Copernicus's work and more about Kepler's own astronomical system. The ''Epitome'' contained all three laws of planetary motion and attempted to explain heavenly motions through physical causes.Gingerich, "Kepler, Johannes" from ''Dictionary of Scientific Biography'', pp. 302–04 Although it explicitly extended the first two laws of planetary motion (applied to Mars in ''Astronomia nova'') to all the planets as well as the Moon and the Medicean satellites of Jupiter, it did not explain how elliptical orbits could be derived from observational data. Originally intended as an introduction for the uninitiated, Kepler sought to model his ''Epitome'' after that of his master
Michael Maestlin Michael Maestlin (also Mästlin, Möstlin, or Moestlin) (30 September 1550 – 26 October 1631) was a German astronomer and mathematician, known for being the mentor of Johannes Kepler. He was a student of Philipp Apian and was known as the te ...

Michael Maestlin
, who published a well-regarded book explaining the basics of geocentric astronomy to non-experts. Kepler completed the first of three volumes, consisting of Books I–III, by 1615 in the same question-answer format of Maestlin's and have it printed in 1617. However, the banning of Copernican books by the Catholic Church, as well as the start of the
Thirty Years' War The Thirty Years' War was a conflict fought largely within the Holy Roman Empire The Holy Roman Empire ( la, Sacrum Romanum Imperium; german: Heiliges Römisches Reich) was a multi-ethnic complex of territories in Western Europe, Weste ...
, meant that publication of the next two volumes would be delayed. In the interim, and to avoid being subject to the ban, Kepler switched the audience of the ''Epitome'' from beginners to that of expert astronomers and mathematicians, as the arguments became more and more sophisticated and requiring advanced mathematics to be understood. The second volume, consisting of Book IV, was published in 1620, followed by the third volume, consisting of Books V–VII, in 1621.


''Rudolphine Tables''

In the years following the completion of ''Astronomia Nova'', most of Kepler's research was focused on preparations for the ''Rudolphine Tables'' and a comprehensive set of
ephemerides In astronomy and celestial navigation, an ephemeris (plural: ephemerides) gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position (and possibly velocity) over time. T ...
(specific predictions of planet and star positions) based on the table (though neither would be completed for many years). Kepler, at last, completed the ''
Rudolphine Tables The ''Rudolphine Tables'' ( la, Tabulae Rudolphinae) consist of a star catalogue and planetary tables published by Johannes Kepler in 1627, using observational data collected by Tycho Brahe (1546–1601). The tables are named in memory of Rudolf ...

Rudolphine Tables
'' in 1623, which at the time was considered his major work. However, due to the publishing requirements of the emperor and negotiations with Tycho Brahe's heir, it would not be printed until 1627.


Astrology

Like
Ptolemy Claudius Ptolemy (; grc-koi, Κλαύδιος Πτολεμαῖος, , ; la, Claudius Ptolemaeus; AD) was a mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Greek: ) includes ...
, Kepler considered astrology as the counterpart to astronomy, and as being of equal interest and value. However, in the following years, the two subjects drifted apart until astrology was no longer practiced among professional astronomers.
Sir Oliver Lodge Sir Oliver Joseph Lodge, (12 June 1851 – 22 August 1940) was a British physicist A physicist is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, are ...

Sir Oliver Lodge
observed that Kepler was somewhat disdainful of astrology in his own day, as he was "continually attacking and throwing sarcasm at astrology, but it was the only thing for which people would pay him, and on it after a fashion he lived." Nonetheless, Kepler spent a huge amount of time trying to restore astrology on a firmer philosophical footing, composing numerous astrological calendars, more than 800 nativities, and a number of treaties dealing with the subject of astrology proper.


''De Fundamentis''

In his bid to become imperial astronomer, Kepler wrote ''De Fundamentis'' (1601), whose title can be translated as “On Giving Astrology Sounder Foundations”, as a short foreword to one of his yearly almanacs. In this work, Kepler describes the effects of the Sun, Moon, and the planets in terms of their light and their influences upon humors, finalizing with Kepler's view that the Earth possesses a soul with some sense of geometry. Stimulated by the geometric convergence of rays formed around it, the Anima mundi, world-soul is sentient but not conscious. As a shepherd is pleased by the piping of a flute without understanding the theory of musical harmony, so likewise Earth responds to the angles and aspects made by the heavens but not in a conscious manner. Eclipses are important as omens because the animal faculty of the Earth is violently disturbed by the sudden intermission of light, experiencing something like emotion and persisting in it for some time. Kepler surmises that there are "cyclic journeys in the humors of the Earth", and gives an example "the 19 year period of the Moon" which sailors say affects tides - presumably the 18.6-year nutation cycle, that is rotation of the lunar nodes - and "if this is so the laws and periods of the cycles should be investigated by collating observations made over many years, something which has not yet been done".


''Tertius Interveniens''

Kepler and Helisaeus Roeslin engaged in a series of published attacks and counter-attacks on the importance of astrology after the supernova of 1604; around the same time, physician Philip Feselius published a work dismissing astrology altogether (and Roeslin's work in particular). In response to what Kepler saw as the excesses of astrology, on the one hand, and overzealous rejection of it, on the other, Kepler prepared ''Tertius Interveniens'' (1610). Nominally this work—presented to the common patron of Roeslin and Feselius—was a neutral mediation between the feuding scholars (the titled meaning "Third-party interventions"), but it also set out Kepler's general views on the value of astrology, including some hypothesized mechanisms of interaction between planets and individual souls. While Kepler considered most traditional rules and methods of astrology to be the "evil-smelling dung" in which "an industrious hen" scrapes, there was an "occasional grain-seed, indeed, even a pearl or a gold nugget" to be found by the conscientious scientific astrologer.


Music


''Harmonice Mundi''

Kepler was convinced "that the geometrical things have provided the Creator with the model for decorating the whole world". In ''Harmonice Mundi'' (1619), he attempted to explain the proportions of the natural world—particularly the astronomical and astrological aspects—in terms of music. The central set of "harmonies" was the ''musica universalis'' or "music of the spheres", which had been studied by Pythagoras,
Ptolemy Claudius Ptolemy (; grc-koi, Κλαύδιος Πτολεμαῖος, , ; la, Claudius Ptolemaeus; AD) was a mathematician A mathematician is someone who uses an extensive knowledge of mathematics Mathematics (from Greek: ) includes ...
and others before Kepler; in fact, soon after publishing ''Harmonice Mundi'', Kepler was embroiled in a priority dispute with Robert Fludd, who had recently published his own harmonic theory. Kepler began by exploring regular polygons and regular solids, including the figures that would come to be known as Kepler-Poinsot polyhedra, Kepler's solids. From there, he extended his harmonic analysis to music, meteorology, and astrology; harmony resulted from the tones made by the souls of heavenly bodies—and in the case of astrology, the interaction between those tones and human souls. In the final portion of the work (Book V), Kepler dealt with planetary motions, especially relationships between orbital speed, orbital velocity and orbital distance from the Sun. Similar relationships had been used by other astronomers, but Kepler—with Tycho's data and his own astronomical theories—treated them much more precisely and attached new physical significance to them. Among many other harmonies, Kepler articulated what came to be known as the third law of planetary motion. He tried many combinations until he discovered that (approximately) "''The square of the periodic times are to each other as the cubes of the mean distances''." Although he gives the date of this epiphany (8 March 1618), he does not give any details about how he arrived at this conclusion. However, the wider significance for planetary dynamics of this purely kinematical law was not realized until the 1660s. When conjoined with Christiaan Huygens' newly discovered law of centrifugal force, it enabled Isaac Newton, Edmund Halley, and perhaps Christopher Wren and Robert Hooke to demonstrate independently that the presumed gravitational attraction between the Sun and its planets decreased with the square of the distance between them. This refuted the traditional assumption of scholastic physics that the power of gravitational attraction remained constant with distance whenever it applied between two bodies, such as was assumed by Kepler and also by Galileo in his mistaken universal law that gravitational fall is uniformly accelerated, and also by Galileo's student Borrelli in his 1666 celestial mechanics.


Optics


''Astronomiae Pars Optica''

As Kepler slowly continued analyzing Tycho's Mars observations—now available to him in their entirety—and began the slow process of tabulating the ''
Rudolphine Tables The ''Rudolphine Tables'' ( la, Tabulae Rudolphinae) consist of a star catalogue and planetary tables published by Johannes Kepler in 1627, using observational data collected by Tycho Brahe (1546–1601). The tables are named in memory of Rudolf ...

Rudolphine Tables
'', Kepler also picked up the investigation of the laws of optics from his lunar essay of 1600. Both lunar and solar eclipses presented unexplained phenomena, such as unexpected shadow sizes, the red color of a total lunar eclipse, and the reportedly unusual light surrounding a total solar eclipse. Related issues of atmospheric refraction applied to ''all'' astronomical observations. Through most of 1603, Kepler paused his other work to focus on optical theory; the resulting manuscript, presented to the emperor on 1 January 1604, was published as ''Astronomiae Pars Optica'' (The Optical Part of Astronomy). In it, Kepler described the inverse-square law governing the intensity of light, reflection by flat and curved mirrors, and principles of pinhole cameras, as well as the astronomical implications of optics such as parallax and the apparent sizes of heavenly bodies. He also extended his study of optics to the human eye, and is generally considered by neuroscientists to be the first to recognize that images are projected inverted and reversed by the Lens (anatomy), eye's lens onto the retina. The solution to this dilemma was not of particular importance to Kepler as he did not see it as pertaining to optics, although he did suggest that the image was later corrected "in the hollows of the brain" due to the "activity of the Soul." Today, ''Astronomiae Pars Optica'' is generally recognized as the foundation of modern optics (though the law of refraction is conspicuously absent). With respect to the beginnings of projective geometry, Kepler introduced the idea of continuous change of a mathematical entity in this work. He argued that if a Focus (geometry), focus of a conic section were allowed to move along the line joining the foci, the geometric form would morph or degenerate, one into another. In this way, an ellipse becomes a parabola when a focus moves toward infinity, and when two foci of an ellipse merge into one another, a circle is formed. As the foci of a hyperbola merge into one another, the hyperbola becomes a pair of straight lines. He also assumed that if a straight line is extended to infinity it will meet itself at a single point at infinity, thus having the properties of a large circle.


''Dioptrice''

In the first months of 1610,
Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (; 15 February 1564 – 8 January 1642) was an Italian astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the ...

Galileo Galilei
—using his powerful new telescope—discovered four satellites orbiting Jupiter. Upon publishing his account as ''Sidereus Nuncius'' [Starry Messenger], Galileo sought the opinion of Kepler, in part to bolster the credibility of his observations. Kepler responded enthusiastically with a short published reply, ''Dissertatio cum Nuncio Sidereo'' [Conversation with the Starry Messenger]. He endorsed Galileo's observations and offered a range of speculations about the meaning and implications of Galileo's discoveries and telescopic methods, for astronomy and optics as well as cosmology and astrology. Later that year, Kepler published his own telescopic observations of the moons in ''Narratio de Jovis Satellitibus'', providing further support of Galileo. To Kepler's disappointment, however, Galileo never published his reactions (if any) to ''Astronomia Nova''. Kepler also started a theoretical and experimental investigation of telescopic lenses using a telescope borrowed from Duke Ernest of Cologne. The resulting manuscript was completed in September 1610 and published as ''Dioptrice'' in 1611. In it, Kepler set out the theoretical basis of double-convex converging lenses and double-concave diverging lenses—and how they are combined to produce a Galilean telescope—as well as the concepts of real image, real vs. virtual image, virtual images, upright vs. inverted images, and the effects of focal length on magnification and reduction. He also described an improved telescope—now known as the ''astronomical'' or ''Keplerian telescope''—in which two convex lenses can produce higher magnification than Galileo's combination of convex and concave lenses.


Mathematics and physics

As a New Year's gift that year (1611), he also composed for his friend and some-time patron, Baron Wackher von Wackhenfels, a short pamphlet entitled ''Strena Seu de Nive Sexangula'' (''A New Year's Gift of Hexagonal Snow''). In this treatise, he published the first description of the hexagonal symmetry of snowflakes and, extending the discussion into a hypothetical atomism, atomistic physical basis for the symmetry, posed what later became known as the Kepler conjecture, a statement about the most efficient arrangement for packing spheres. Kepler wrote the influential mathematical treatise ''Nova stereometria doliorum vinariorum'' in 1613, on measuring the volume of containers such as wine barrels, which was published in 1615. Kepler also contributed to the development of infinitesimal methods and numerical analysis, including iterative approximations, infinitesimals, and the early use of logarithms and transcendental equations.


Legacy


Reception of his astronomy

Kepler's laws of planetary motion were not immediately accepted. Several major figures such as Galileo and René Descartes completely ignored Kepler's ''Astronomia nova.'' Many astronomers, including Kepler's teacher, Michael Maestlin, objected to Kepler's introduction of physics into his astronomy. Some adopted compromise positions. Ismaël Bullialdus accepted elliptical orbits but replaced Kepler's area law with uniform motion in respect to the empty focus of the ellipse, while Seth Ward (bishop), Seth Ward used an elliptical orbit with motions defined by an equant. Several astronomers tested Kepler's theory, and its various modifications, against astronomical observations. Two transits of Venus and Mercury across the face of the sun provided sensitive tests of the theory, under circumstances when these planets could not normally be observed. In the case of the transit of Mercury in 1631, Kepler had been extremely uncertain of the parameters for Mercury, and advised observers to look for the transit the day before and after the predicted date. Pierre Gassendi observed the transit on the date predicted, a confirmation of Kepler's prediction. This was the first observation of a transit of Mercury. However, his attempt to observe the transit of Venus just one month later was unsuccessful due to inaccuracies in the Rudolphine Tables. Gassendi did not realize that it was not visible from most of Europe, including Paris. Jeremiah Horrocks, who observed the Transit of Venus, 1639, 1639 Venus transit, had used his own observations to adjust the parameters of the Keplerian model, predicted the transit, and then built apparatus to observe the transit. He remained a firm advocate of the Keplerian model. ''Epitome of Copernican Astronomy'' was read by astronomers throughout Europe, and following Kepler's death, it was the main vehicle for spreading Kepler's ideas. In the period 1630 – 1650, this book was the most widely used astronomy textbook, winning many converts to ellipse-based astronomy. However, few adopted his ideas on the physical basis for celestial motions. In the late 17th century, a number of physical astronomy theories drawing from Kepler's work—notably those of Giovanni Alfonso Borelli and Robert Hooke—began to incorporate attractive forces (though not the quasi-spiritual motive species postulated by Kepler) and the Cartesian concept of Principle of inertia (physics), inertia. This culminated in Isaac Newton's ''Philosophiae Naturalis Principia Mathematica, Principia Mathematica'' (1687), in which Newton derived Kepler's laws of planetary motion from a force-based theory of
universal gravitation Newton's law of universal gravitation is usually stated as that every particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can ...
.


History of science

Beyond his role in the historical development of astronomy and natural philosophy, Kepler has loomed large in the philosophy of science, philosophy and historiography of science. Kepler and his laws of motion were central to early histories of astronomy such as Jean-Étienne Montucla's 1758 ''Histoire des mathématiques'' and Jean-Baptiste Delambre's 1821 ''Histoire de l'astronomie moderne''. These and other histories written from an Age of Enlightenment, Enlightenment perspective treated Kepler's metaphysical and religious arguments with skepticism and disapproval, but later Romanticism in science, Romantic-era natural philosophers viewed these elements as central to his success. William Whewell, in his influential ''History of the Inductive Sciences'' of 1837, found Kepler to be the archetype of the inductive scientific genius; in his ''Philosophy of the Inductive Sciences'' of 1840, Whewell held Kepler up as the embodiment of the most advanced forms of scientific method. Similarly, Ernst Friedrich Apelt—the first to extensively study Kepler's manuscripts, after their purchase by Catherine the Great—identified Kepler as a key to the "Scientific revolution, Revolution of the sciences". Apelt, who saw Kepler's mathematics, aesthetic sensibility, physical ideas, and theology as part of a unified system of thought, produced the first extended analysis of Kepler's life and work. Alexandre Koyré's work on Kepler was, after Apelt, the first major milestone in historical interpretations of Kepler's cosmology and its influence. In the 1930s and 1940s, Koyré, and a number of others in the first generation of professional historians of science, described the "
Scientific Revolution The Scientific Revolution was a series of events that marked the emergence of modern science during the early modern period, when developments in History of mathematics#Mathematics during the Scientific Revolution, mathematics, History of phys ...

Scientific Revolution
" as the central event in the history of science, and Kepler as a (perhaps the) central figure in the revolution. Koyré placed Kepler's theorization, rather than his empirical work, at the center of the intellectual transformation from ancient to modern world-views. Since the 1960s, the volume of historical Kepler scholarship has expanded greatly, including studies of his astrology and meteorology, his geometrical methods, the role of his religious views in his work, his literary and rhetorical methods, his interaction with the broader cultural and philosophical currents of his time, and even his role as an historian of science. Philosophers of science—such as Charles Sanders Peirce, Norwood Russell Hanson, Stephen Toulmin, and Karl Popper—have repeatedly turned to Kepler: examples of Commensurability (philosophy of science), incommensurability, analogical reasoning, falsification, and many other philosophical concepts have been found in Kepler's work. Physicist Wolfgang Pauli even used Kepler's priority dispute with Robert Fludd to explore the implications of analytical psychology on scientific investigation.


Editions and translations

Modern translations of a number of Kepler's books appeared in the late-nineteenth and early-twentieth centuries, the systematic publication of his collected works began in 1937 (and is nearing completion in the early 21st century). An edition in eight volumes, '' Kepleri Opera omnia,'' was prepared by Christian Frisch (1807–1881), during 1858 to 1871, on the occasion of Kepler's 300th birthday. Frisch's edition only included Kepler's Latin, with a Latin commentary. A new edition was planned beginning in 1914 by Walther von Dyck (1856–1934). Dyck compiled copies of Kepler's unedited manuscripts, using international diplomatic contacts to convince the Soviet authorities to lend him the manuscripts kept in Leningrad for photographic reproduction. These manuscripts contained several works by Kepler that had not been available to Frisch. Dyck's photographs remain the basis for the modern editions of Kepler's unpublished manuscripts. Max Caspar (1880–1956) published his German translation of Kepler's ''Mysterium Cosmographicum'' in 1923. Both Dyck and Caspar were influenced in their interest in Kepler by mathematician Alexander von Brill (1842–1935). Caspar became Dyck's collaborator, succeeding him as project leader in 1934, establishing the ''Kepler-Kommission'' in the following year. Assisted by Martha List (1908–1992) and Franz Hammer (1898–1979), Caspar continued editorial work during World War II. Max Caspar also published a biography of Kepler in 1948. The commission was later chaired by Volker Bialas (during 1976–2003) and Ulrich Grigull (during 1984–1999) and Roland Bulirsch (1998–2014).


Veneration and eponymy

Kepler has acquired a popular image as an icon of scientific modernity and a man before his time; science popularizer Carl Sagan described him as "the first astrophysics, astrophysicist and the last scientific astrologer". The debate over Kepler's place in the Scientific Revolution has produced a wide variety of philosophical and popular treatments. One of the most influential is Arthur Koestler's 1959 ''The Sleepwalkers (Koestler book), The Sleepwalkers'', in which Kepler is unambiguously the hero (morally and theologically as well as intellectually) of the revolution. A well-received, if fanciful, historical novel by John Banville, ''Kepler'' (1981), explored many of the themes developed in Koestler's non-fiction narrative and in the philosophy of science. Somewhat more fanciful is a recent work of nonfiction, ''Heavenly Intrigue'' (2004), suggesting that Kepler murdered Tycho Brahe to gain access to his data. In Austria, Kepler left behind such a historical legacy that he was one of the motifs of a silver collector's coin: the Euro gold and silver commemorative coins (Austria)#2002 coinage, 10-euro Johannes Kepler silver coin, minted on 10 September 2002. The reverse side of the coin has a portrait of Kepler, who spent some time teaching in Graz and the surrounding areas. Kepler was acquainted with personally, and he probably influenced the construction of Eggenberg Castle (the motif of the obverse of the coin). In front of him on the coin is the model of nested spheres and polyhedra from ''Mysterium Cosmographicum''. The German composer Paul Hindemith wrote an opera about Kepler entitled ''Die Harmonie der Welt'', and a symphony of the same name was derived from music for the opera. Philip Glass wrote an opera called ''Kepler (opera), Kepler'' based on Kepler's life (2009). Kepler is honored together with Nicolaus Copernicus with a feast day on the Calendar of saints (Episcopal Church in the United States of America), liturgical calendar of the Episcopal Church (USA) on 23 May. Directly named for Kepler's contribution to science are Kepler's laws of planetary motion, Kepler's Supernova (Supernova 1604, which he observed and described) and the Kepler-Poinsot polyhedra, Kepler Solids, a set of geometrical constructions, two of which were described by him, and the Kepler conjecture on sphere packing. * In astronomy: The lunar crater Kepler (lunar crater), Kepler (''Keplerus'', named by Giovanni Riccioli, 1651), the asteroid 1134 Kepler (1929), Kepler (crater on Mars) (1973), Kepler Launch Site for model rockets (2001), the Kepler space telescope, a space photometer launched by NASA in 2009, Johannes Kepler ATV, ''Johannes Kepler'' ATV (Automated Transfer Vehicle launched to resupply the International Space Station, ISS in 2011). * Educational institutions: Johannes Kepler University Linz (1975), Kepler College (Seattle, Washington), besides several institutions of primary and secondary education, such as Johannes Kepler Grammar School, at the site where Kepler lived in Prague, and ''Kepler Gymnasium'', Tübingen * Streets or squares named after him: Keplerplatz Vienna (station of Vienna U-Bahn), Keplerstraße in Hanau near Frankfurt am Main, Keplerstraße in Gera, Keplerstraße in Munich, Germany, Keplerstraße and Keplerbrücke in Graz, Austria, Keplerova ulice in Prague, ulitsa Keplera in Verkhnetemernitsky near Rostov-on-Don, Russia. * The Kepler Mountains and Kepler Track in Fiordland National Park, South Island, New Zealand; Kepler Challenge (1988). * Kepler (microarchitecture), Kepler, a high end graphics processing microarchitecture introduced by Nvidia in 2012.


Works

* '' Mysterium Cosmographicum'' (''The Sacred Mystery of the Cosmos'') (1596) * ''De Fundamentis Astrologiae Certioribus'' (
On Firmer Fundaments of Astrology
'; 1601) * * ''De Stella Nova, De Stella nova in pede Serpentarii'' (''On the New Star in Ophiuchus's Foot'') (1606) * ''
Astronomia nova ''Astronomia nova'' (English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually become ...

Astronomia nova
'' (''New Astronomy'') (1609) * ''Tertius Interveniens'' (''Third-party Interventions'') (1610) * ''Dissertatio cum Nuncio Sidereo'' (''Conversation with the Starry Messenger'') (1610) * ''Dioptrice'' (1611) * ''De nive sexangula'' (''On the Six-Cornered Snowflake'') (1611)
English translation on Google Books preview
* ''De vero Anno, quo aeternus Dei Filius humanam naturam in Utero benedictae Virginis Mariae assumpsit'' (1614)"... in 1614, Johannes Kepler published his book ''De vero anno quo aeternus dei filius humanum naturam in utero benedictae Virginis Mariae assumpsit'', on the chronology related to the Star of Bethlehem."
The Star of Bethlehem
Kapteyn Astronomical Institute
* ''Eclogae Chronicae'' (1615, published with ''Dissertatio cum Nuncio Sidereo'') * ''Nova stereometria doliorum vinariorum'' (''New Stereometry of Wine Barrels'') (1615)
''Ephemerides nouae motuum coelestium'' (1617–30)
* * ** ** * * ''
Harmonice Mundi ''Harmonices Mundi''The full title is ''Ioannis Keppleri Harmonices mundi libri V'' (''The Five Books of Johannes Kepler's The Harmony of the World''). (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic ...
'' (''Harmony of the Worlds'') (1619)
English translation on Google Books
* ''Mysterium cosmographicum'' (''The Sacred Mystery of the Cosmos''), 2nd edition (1621) * ''Rudolphine Tables, Tabulae Rudolphinae'' (''Rudolphine Tables'') (1627) * '' Somnium''
''The Dream''
(1634)
English translation on Google Books preview
* ** ** ** ** ** ** ** ** A critical edition of Kepler's collected works (''Johannes Kepler Gesammelte Werke'', KGW) in 22 volumes is being edited by the ''Kepler-Kommission'' (founded 1935) on behalf of the Bayerische Akademie der Wissenschaften. :Vol. 1: ''Mysterium Cosmographicum. De Stella Nova''. Ed. M. Caspar. 1938, 2nd ed. 1993. Paperback . :Vol. 2: ''Astronomiae pars optica''. Ed. F. Hammer. 1939, Paperback . :Vol. 3: Astronomia Nova. Ed. M. Caspar. 1937. IV, 487 p. 2. ed. 1990. Paperback . Semi-parchment . :Vol. 4: ''Kleinere Schriften 1602–1611. Dioptrice''. Ed. M. Caspar, F. Hammer. 1941. . :Vol. 5: ''Chronologische Schriften''. Ed. F. Hammer. 1953. Out-of-print. :Vol. 6: ''Harmonice Mundi''. Ed. M. Caspar. 1940, 2nd ed. 1981, . :Vol. 7: ''Epitome Astronomiae Copernicanae''. Ed. M. Caspar. 1953, 2nd ed. 1991. , Paperback . :Vol. 8: ''Mysterium Cosmographicum. Editio altera cum notis. De Cometis. Hyperaspistes''. Commentary F. Hammer. 1955. Paperback . :Vol 9: ''Mathematische Schriften''. Ed. F. Hammer. 1955, 2nd ed. 1999. Out-of-print. :Vol. 10: ''Tabulae Rudolphinae''. Ed. F. Hammer. 1969. . :Vol. 11,1: ''Ephemerides novae motuum coelestium''. Commentary V. Bialas. 1983. , Paperback . :Vol. 11,2: ''Calendaria et Prognostica. Astronomica minora. Somnium''. Commentary V. Bialas, H. Grössing. 1993. , Paperback . :Vol. 12: ''Theologica. Hexenprozeß. Tacitus-Übersetzung. Gedichte''. Commentary J. Hübner, H. Grössing, F. Boockmann, F. Seck. Directed by V. Bialas. 1990. , Paperback . * Vols. 13–18: Letters: ::Vol. 13: ''Briefe 1590–1599''. Ed. M. Caspar. 1945. 432 p. . ::Vol. 14: ''Briefe 1599–1603''. Ed. M. Caspar. 1949. Out-of-print. 2nd ed. in preparation. ::Vol 15: ''Briefe 1604–1607''. Ed. M. Caspar. 1951. 2nd ed. 1995. . ::Vol. 16: ''Briefe 1607–1611''. Ed. M. Caspar. 1954. . ::Vol. 17: ''Briefe 1612–1620''. Ed. M. Caspar. 1955. . ::Vol. 18: ''Briefe 1620–1630''. Ed. M. Caspar. 1959. . :Vol. 19: ''Dokumente zu Leben und Werk''. Commentary M. List. 1975. . :Vols. 20–21: manuscripts ::Vol. 20,1: ''Manuscripta astronomica (I). Apologia, De motu Terrae, Hipparchus etc.'' Commentary V. Bialas. 1988. . Paperback . ::Vol. 20,2: ''Manuscripta astronomica (II). Commentaria in Theoriam Martis''. Commentary V. Bialas. 1998. Paperback . ::Vol. 21,1: ''Manuscripta astronomica (III) et mathematica. De Calendario Gregoriano''. In preparation. ::Vol. 21,2: ''Manuscripta varia''. In preparation. :Vol. 22: General index, in preparation. The Kepler-Kommission also publishes ''Bibliographia Kepleriana'' (2nd ed. List, 1968), a complete bibliography of editions of Kepler's works, with a supplementary volume to the second edition (ed. Hamel 1998).


See also

* Cavalieri's principle * History of astronomy * History of physics ** Kepler orbit ** Kepler problem ** Kepler triangle * Kepler–Bouwkamp constant * Penrose tiling * Radiation pressure * Rhombicosidodecahedron * Rhombicuboctahedron * Simpson's rule * Stellated octahedron


Notes


References


Citations


Sources

* Andersen, Hanne; Peter Barker; and Xiang Chen. ''The Cognitive Structure of Scientific Revolutions'', chapter 6: "The Copernican Revolution." New York: Cambridge University Press, 2006. * Armitage, Angus. ''John Kepler'', Faber, 1966. * Banville, John. ''Kepler'', Martin, Secker and Warburg, London, 1981 (fictionalised biography) * Barker, Peter and Bernard R. Goldstein: "Theological Foundations of Kepler's Astronomy". ''Osiris'', Volume 16. ''Science in Theistic Contexts.'' University of Chicago Press, 2001, pp.  88–113 * Caspar, Max. ''Kepler''; transl. and ed. by C. Doris Hellman; with a new introduction and references by Owen Gingerich; bibliographic citations by Owen Gingerich and Alain Segonds. New York: Dover, 1993. * Connor, James A. ''Kepler's Witch: An Astronomer's Discovery of Cosmic Order Amid Religious War, Political Intrigue, and the Heresy Trial of His Mother''. HarperSanFrancisco, 2004. * De Gandt, Francois. ''Force and Geometry in Newton's'' Principia, Translated by Curtis Wilson, Princeton University Press, 1995. * J. L. E. Dreyer, Dreyer, J. L. E. ''A History of Astronomy from Thales to Kepler''. Dover Publications Inc, 1967. * Ferguson, Kitty. ''The nobleman and his housedog: Tycho Brahe and Johannes Kepler: the strange partnership that revolutionized science.'' London: Review, 2002. – published in the US as: ''Tycho & Kepler: the unlikely partnership that forever changed our understanding of the heavens.'' New York: Walker, 2002. * Judith V. Field, Field, J. V.. ''Kepler's geometrical cosmology''. University of Chicago Press, 1988. * Gilder, Joshua and Anne-Lee Gilder: ''Heavenly Intrigue: Johannes Kepler, Tycho Brahe, and the Murder Behind One of History's Greatest Scientific Discoveries'', Doubleday (18 May 2004). Review
bookpage.com
* Owen Gingerich, Gingerich, Owen. ''The Eye of Heaven: Ptolemy, Copernicus, Kepler''. American Institute of Physics, 1993. (Masters of modern physics; v. 7) * Gingerich, Owen: "Kepler, Johannes" in ''Dictionary of Scientific Biography'', Volume VII. Charles Coulston Gillispie, editor. New York: Charles Scribner's Sons, 1973 * Greenbaum and Boockmann: "Kepler's Astrology", ''Culture and Cosmos'' Vol. 14. Special Double Issue, 2012. * Jardine, Nick: "Koyré's Kepler/Kepler's Koyré," ''History of Science'', Vol. 38 (2000), pp.  363–376 * Kepler, Johannes. ''Johannes Kepler New Astronomy'' trans. W. Donahue, foreword by O. Gingerich, Cambridge University Press 1993. * Kepler, Johannes and Christian Frisch. ''Joannis Kepleri Astronomi Opera Omnia'' (''John Kepler, Astronomer; Complete Works''), 8 vols.(1858–1871).
vol. 1, 1858vol. 2, 1859vol. 3, 1860vol. 6, 1866vol. 7, 1868
Frankfurt am Main and Erlangen, Heyder & Zimmer, – Google Books * Kepler, Johannes, et al. ''Great Books of the Western World. Volume 16: Ptolemy, Copernicus, Kepler'', Chicago: Encyclopædia Britannica, Inc., 1952. (contains English translations by of Kepler's ''Epitome'', Books IV & V and ''Harmonice'' Book 5) * Arthur Koestler, Koestler, Arthur. ''The Sleepwalkers (Koestler book), The Sleepwalkers: A History of Man's Changing Vision of the Universe.'' (1959). * Alexandre Koyré, Koyré, Alexandre: ''Galilean Studies'' Harvester Press, 1977. * Koyré, Alexandre: ''The Astronomical Revolution: Copernicus-Kepler-Borelli'' Ithaca, NY: Cornell University Press, 1973. ; Methuen, 1973. ; Hermann, 1973. * Thomas Samuel Kuhn, Kuhn, Thomas S. ''The Copernican Revolution: Planetary Astronomy in the Development of Western Thought''. Cambridge, MA: Harvard University Press, 1957. * Lindberg, David C.: "The Genesis of Kepler's Theory of Light: Light Metaphysics from Plotinus to Kepler." ''Osiris'', N.S. 2. University of Chicago Press, 1986, pp.  5–42. * Lear, John. ''Kepler's Dream''. Berkeley: University of California Press, 1965 * M.T.K Al-Tamimi. "Great collapse Kepler's first law", ''Natural Science'', 2 (2010), * North, John. ''The Fontana History of Astronomy and Cosmology,'' Fontana Press, 1994. * Pannekoek, Anton: ''A History of Astronomy'', Dover Publications Inc 1989. * Wolfgang Pauli, Pauli, Wolfgang. ''Wolfgang Pauli – Writings on physics and philosophy'', translated by Robert Schlapp and edited by P. Enz and Karl von Meyenn (Springer Verlag, Berlin, 1994). See section 21, ''The influence of archetypical ideas on the scientific theories of Kepler'', concerning Johannes Kepler and Robert Fludd (1574–1637). * Schneer, Cecil: "Kepler's New Year's Gift of a Snowflake." ''Isis (journal), Isis'', Volume 51, No. 4. University of Chicago Press, 1960, pp.  531–545. * Shapin, Steven. ''The Scientific Revolution''. Chicago: University of Chicago Press, 1996. * Stephenson, Bruce. ''Kepler's physical astronomy''. New York: Springer, 1987. (Studies in the history of mathematics and physical sciences; 13); reprinted Princeton:Princeton Univ. Pr., 1994. * Stephenson, Bruce. ''The Music of the Heavens: Kepler's Harmonic Astronomy'', Princeton University Press, 1994. * Toulmin, Stephen and June Goodfield. ''The Fabric of the Heavens: The Development of Astronomy and Dynamics''. Pelican, 1963. * Voelkel, James R. ''The Composition of Kepler's Astronomia nova'', Princeton University Press, 2001. * Richard S. Westfall, Westfall, Richard S.. ''The Construction of Modern Science: Mechanism and Mechanics''. John Wiley and Sons, 1971. ; reprinted Cambridge University Press, 1978. * Westfall, Richard S. ''Never at Rest: A Biography of Isaac Newton''. Cambridge University Press, 1981. * Wolf, A. ''A History of Science, Technology and Philosophy in the 16th and 17th centuries''. George Allen & Unwin, 1950.


External links


Kepler's Conversation with the Starry Messenger (English translation of ''Dissertation cum Nuncio Sidereo'')


* * * [http://emlo.bodleian.ox.ac.uk/blog/?catalogue=johannes-kepler The Correspondence of Johannes Kepler] i
EMLO
* * Full text of by Walter Bryant (public domain biography)
JohannesKepler.Info
Kepler information and community website, launched on 27 December 2009
''Harmonice mundi''
("The Harmony of the Worlds") in fulltext facsimile; Carnegie-Mellon University *
The Correspondence of Johannes Kepler
i
EMLO
* (1920 book, part of ''Men of Science'' series) * * Plant, David

*
Online Galleries, History of Science Collections, University of Oklahoma Libraries
High resolution images of works by and/or portraits of Johannes Kepler in .jpg and .tiff format.

at the Library of Congress: * Books by Johannes Kepler that are available in digital facsimile from the website of the Linda Hall Library: ** (1604
''Ad vitellionem paralipomena''
** (1606
''De stella nova in pede Serpentarii''
** (1611
''Dioptrice''
** (1618
''Epitome astronomiae Copernicanæ''
{{DEFAULTSORT:Kepler, Johannes Johannes Kepler, 1571 births 1630 deaths People from Weil der Stadt 16th-century German writers 16th-century German male writers 17th-century German writers 17th-century German male writers 16th-century Latin-language writers 16th-century German mathematicians 17th-century Latin-language writers 17th-century German mathematicians 17th-century German novelists German expatriates in Austria German expatriates in the Czech lands Scientists from Prague Austrian Lutherans Christian astrologers German cosmologists German astrologers 17th-century German astronomers German Lutherans Anglican saints German music theorists Natural philosophers Copernican Revolution Mathematicians from Prague Members of the Lincean Academy Writers about music University of Tübingen alumni 17th-century German philosophers 16th-century German astronomers