Johannes Kepler was born in Weil der Stadt in Swabia, in southwest Germany.
His paternal grandfather, Sebald Kepler, was a respected craftsman who served as
mayor of the city; his maternal grandfather, Melchior Guldenmann, was an innkeeper and
mayor of the nearby village of Eltingen. His father, Heinrich Kepler, was "an immoral,
rough and quarrelsome soldier," according to Kepler, and he described his mother in
similar unflattering terms. From 1574 to 1576 Johannes lived with his grandparents;
in 1576 his parents moved to nearby Leonberg, where Johannes entered the Latin
school. In 1584 he entered the Protestant seminary at Adelberg, and in 1589 he
began his university education at the Protestant university of Tübingen.
Here he studied theology and read widely. He passed the M.A. examination in 1591
and continued his studies as a graduate student.
Kepler's teacher in the mathematical subjects was Michael Maestlin
(1580-1635). Maestlin was one of the earliest astronomers to subscribe to
Nicolaus Copernicus's heliocentric theory, although in his university lectures he
taught only the Ptolemaic system. Only in what we might call graduate
seminars did he acquaint his students, among whom was Kepler, with the
technical details of the
Copernican system. Kepler stated later that at this time he
became a Copernican for "physical or, if you prefer, metaphysical reasons."
In 1594 Kepler accepted an appointment as professor of mathematics at
the Protestant seminary in Graz (in the Austrian province of Styria).
He was also appointed district mathematician and calendar maker. Kepler
remained in Graz until 1600, when all Protestants were forced to convert
to Catholicism or leave the province, as part of Counter Reformation
measures. For six years, Kepler taught arithmetic, geometry (when there
were interested students), Virgil, and rhetoric. In his spare time he
pursued his private studies in astronomy and astrology. In 1597 Kepler
married Barbara Müller. In that same year he published his first
important work, The Cosmographic Mystery, in which he argued that
the distances of the planets from the Sun in the Copernican system were
determined by the five regular solids, if one supposed that a planet's
orbit was circumscribed about one solid and inscribed in another.
Except for Mercury, Kepler's construction produced remarkably accurate
results. Because of his talent as a mathematician, displayed in this
volume, Kepler was invited by
Tycho Brahe to Prague to become his assistant and calculate new
orbits for the planets from Tycho's observations. Kepler moved to Prague in 1600.
Kepler served as Tycho Brahe's assistant until the latter's death in
1601 and was then appointed Tycho's successor as Imperial Mathematician, the most
prestigious appointment in mathematics in Europe. He occupied this post until,
in 1612, Emperor Rudolph II was deposed. In Prague Kepler published a number of
important books. In 1604 Astronomia pars Optica ("The Optical Part of
Astronomy") appeared, in which he treated atmospheric refraction but also
treated lenses and gave the modern explanation of the workings of the eye; in
1606 he published De Stella Nova ("Concerning the New Star") on the new
star that had appeared in 1604; and in 1609 his Astronomia Nova ("New
Astronomy") appeared, which contained his first two laws (planets move in
elliptical orbits with the sun as one of the foci, and a planet sweeps out
equal areas in equal times). Whereas other astronomers still followed the
ancient precept that the study of the planets is a problem only in kinematics,
Kepler took an openly dynamic approach, introducing physics into the heavens.
In 1610 Kepler heard and read about Galileo's discoveries with the
spyglass. He quickly composed a long letter of support which he published
as Dissertatio cum Nuncio Sidereo ("Conversation with the Sidereal
Messenger"), and when, later that year, he obtained the use of a suitable
telescope, he published his observations of Jupiter's satellites under the
title Narratio de Observatis Quatuor Jovis Satellitibus ("Narration
about Four Satellites of Jupiter observed"). These tracts were an enormous
support to Galileo, whose discoveries were doubted or denied by many. Both
of Kepler's tracts were quickly reprinted in Florence. Kepler went on to
provide the beginning of a theory of the telescope in his Dioptrice,
published in 1611.
During this period the Keplers had three children (two had been
born in Graz but died within months), Susanna (1602), who married Kepler's
assistant Jakob Bartsch in 1630, Friedrich (1604-1611), and Ludwig (1607-1663).
Kepler's wife, Barbara, died in 1612. In that year Kepler accepted the position
of district mathematician in the city of Linz, a position he occupied until
1626. In Linz Kepler married Susanna Reuttinger. The couple had six children,
of whom three died very early.
In Linz Kepler published first a work on chronology and the year of Jesus's
birth, In German in 1613 and more amply in Latin in 1614: De Vero Anno quo
Aeternus Dei Filius Humanam Naturam in Utero Benedictae Virginis Mariae Assumpsit
(Concerning the True Year in which the Son of God assumed a Human Nature in the
Uterus of the Blessed Virgin Mary"). In this work Kepler demonstrated that the
Christian calendar was in error by five years, and that Jesus had been born in 4 BC,
a conclusion that is now universally accepted. Between 1617 and 1621 Kepler published
Epitome Astronomiae Copernicanae ("Epitome of Copernican Astronomy"), which
became the most influential introduction to heliocentric astronomy; in 1619 he published
Harmonice Mundi ("Harmony of the World"), in which he derived the heliocentric
distances of the planets and their periods from considerations of musical harmony.
In this work we find his third law, relating the periods of the planets to their mean
In 1615-16 there was a witch hunt in Kepler's native region, and his own
mother was accused of being a witch. It was not until late in 1620 that the
proceedings against her ended with her being set free. At her trial, her defense
was conducted by her son Johannes.
1618 marked the beginning of the Thirty Years War, a war that devastated
the German and Austrian region. Kepler's position in Linz now became progressively
worse, as Counter Reformation Counter Reformation measures put pressure on Protestants in the Upper
Austria province of which Linz was the capital. Because he was a court official, Kepler
was exempted from a decree that banished all Protestants from the province, but he
nevertheless suffered persecution. During this time Kepler was having his Tabulae
Rudolphinae ("Rudolphine Tables") printed, the new tables, based on Tycho Brahe's
accurate observations, calculated according to Kepler's elliptical astronomy. When
a peasant rebellion broke out and Linz was besieged, a fire destroyed the printer's
house and shop, and with it much of the printed edition. Soldiers were garrisoned
in Kepler's house. He and his family left Linz in 1626. The Tabulae Rudolphinae
were published in Ulm in 1627.
Kepler now had no position and no salary. He tried to obtain appointments
from various courts and returned to Prague in an effort to pry salary that was owed
him from his years as Imperial Mathemati
Johannes Kepler alizaliwa huko Weil der Stadt huko Swabia, kusini-magharibi mwa Ujerumani. Baba yake mkubwa, Sebald Kepler, alikuwa fundi wa sanaa aliyeheshimiwa ambaye alitumikia kama meya wa mji; babu yake wa mama, Melchior Guldenmann, alikuwa mwenye nyumba ya wageni na meya wa kijiji cha karibu cha Eltingen. "Keppler aliandika kwamba baba yake, Heinrich Kepler, alikuwa ""soldati asiye na adili, mkali na mwenye ugomvi,"" na alifafanua mama yake kwa maneno yasiyo ya kupendeza kama hayo." Katika mwaka wa 1574 na 1576 Johannes aliishi na babu na nyanya yake, na mwaka wa 1576 wazazi wake walihamia Leonberg, ambako Johannes aliingia shule ya Kilatini. Mwaka 1584 aliingia katika seminari ya Kiprotestanti huko Adelberg, na mwaka 1589 alianza masomo yake ya chuo kikuu katika chuo kikuu cha Kiprotestanti cha Tübingen. Huko alisoma theolojia na kusoma sana. Alihitimu shahada ya uzamili. Alihitimu katika mwaka wa 1591 na akaendelea na masomo yake ya shahada ya kwanza. Mwalimu wa Kepler katika masomo ya hisabati alikuwa Michael Maestlin (1580-1635). Maestlin alikuwa mmoja wa wanaastronomia wa kwanza kuunga mkono nadharia ya Nicolaus Copernicus ya heliocentric, ingawa katika mihadhara yake ya chuo kikuu alifundisha tu mfumo wa Ptolemaic. Katika semina za kuhitimu, Kepler aliwafundisha wanafunzi wake mambo ya kiufundi kuhusu mfumo wa Copernicus. Baadaye Kepler alisema kwamba wakati huo akawa Mkoperniko kwa "sababu za kimwili au, ikiwa unapendelea, za kimetaphysical". Mwaka 1594 Kepler alikubali kuwa profesa wa hisabati katika seminari ya Kiprotestanti huko Graz, katika jimbo la Styria, Austria. Pia aliteuliwa kuwa mtaalamu wa hesabu wa wilaya na mtengenezaji wa kalenda. Kepler alikaa Graz hadi mwaka 1600, wakati Waprotestanti wote walipowalazimishwa kugeuka kuwa Wakatoliki au kuondoka mkoa huo, kama sehemu ya hatua za Counter-Reformation. Kwa miaka sita, Kepler alifundisha hesabu, jiometri (wakati kulikuwa na wanafunzi waliopendezwa), Virgil, na usemi. Katika wakati wake wa kupumzika aliendelea na masomo yake ya kibinafsi katika elimu ya nyota na unajimu. Mwaka 1597 Kepler aliolewa na Barbara Müller. Katika mwaka huohuo, alichapisha kazi yake ya kwanza muhimu, The Cosmographic Mystery, ambayo alidai kwamba umbali wa sayari kutoka kwa Jua katika mfumo wa Copernicus ulibainishwa na solids tano za kawaida, ikiwa mtu angedhani kwamba mzunguko wa sayari ulizungukwa na moja na kuandikwa katika nyingine. Isipokuwa kwa Mercury, ujenzi wa Kepler ulitoa matokeo sahihi sana. Kepler alikuwa na uwezo wa kuunda mfumo wa sayari, na kwa sababu ya uwezo wake wa kuunda mfumo wa hesabu, alipewa na Tycho Brahe mwaliko wa kwenda Prague ili awe msaidizi wake na kuhesabu mizunguko mpya ya sayari kutokana na uchunguzi wa Tycho. Kepler alihamia Prague mwaka 1600. Kepler alitumikia kama msaidizi wa Tycho Brahe hadi kifo chake mwaka 1601 na baadaye aliteuliwa kuwa mrithi wa Tycho kama Imperial Mathematician, uteuzi wa kifahari zaidi katika hisabati huko Ulaya. Alitumikia katika cheo hicho hadi mwaka 1612 wakati Mfalme Rudolf wa Pili alipopinduliwa. Huko Prague Kepler alichapisha vitabu kadhaa muhimu. "Astronomia Pars Optica (1604) ilisema kwamba ""mwisho wa siku, wakati wa mwangaza wa jua, sayari zote zinatembea katika mizunguko ya elliptical na jua ni moja ya vituo, na sayari husafiri katika maeneo sawa katika muda sawa.""" Wakati wataalamu wengine wa nyota waliendelea kufuata kanuni ya kale ya kwamba utafiti wa sayari ni tatizo tu katika kinematics, Kepler alichukua mbinu ya wazi nguvu, kuanzisha fizikia katika mbingu. Katika mwaka wa 1610 Kepler alisoma na kusikia habari kuhusu uvumbuzi wa Galileo wa kutumia kioo cha macho. "Alichapisha barua yake ya kwanza ya kuunga mkono ""Dissertatio cum Nunzio Sidereo"" na baadaye mwaka huo alipopata kutumia darubini inayofaa, alichapisha uchunguzi wake wa satelaiti za Jupita chini ya kichwa ""Narration de Quartus Jovianus.""" Vitabu hivyo vilimsaidia sana Galileo, ambaye watu wengi walitilia shaka au kukataa uvumbuzi wake. Trakti zote mbili za Kepler zilichapishwa tena upesi huko Florence. Kepler aliandika kitabu chake Dioptria mwaka 1611. Katika kipindi hicho, familia ya Kepler ilikuwa na watoto watatu (wawili walikuwa wamezaliwa Graz lakini walikufa baada ya miezi michache), Susanna (1602), ambaye aliolewa na msaidizi wa Kepler Jakob Bartsch (1630-1611), na Ludwig (1607-1663). Mke wa Kepler, Barbara, alikufa mwaka wa 1612. Kepler alitumikia akiwa mtaalamu wa hesabu katika mji wa Linz, Ujerumani, hadi mwaka wa 1626. Katika Linz Kepler aliolewa na Susanna Reuttinger. Wenzi hao walikuwa na watoto sita, ambao watatu kati yao walikufa mapema sana. "Keppler aliandika kitabu chake cha kwanza cha ""De Verum Anno Quo Aeternus Dei Filius Humanum Naturam in Utero Benedictae Virginis Mariae Assumpti"" mwaka 1613." Kepler alionyesha kwamba kalenda ya Kikristo ilikuwa na makosa ya miaka mitano na kwamba Yesu alizaliwa mwaka wa 4 KK, jambo ambalo sasa linakubaliwa ulimwenguni pote. "Kipindi cha 1617 na 1621 Kepler alichapisha ""Epitome Astronomi Copernicus"" (Epitome of Copernican Astronomy), ambayo ilikuwa ni utangulizi wa kihistoria wa elimu ya nyota ya jua, na mwaka 1619 alichapisha ""Harmony Mundi"" (Harmony of the World), ambayo ilitoa umbali wa jua na sayari na vipindi vyao kutokana na kuzingatia mwelekeo wa muziki." Katika kitabu chake cha Kepler, alitoa sheria ya tatu ya kuunganisha vipindi vya sayari na wastani wao, na katika mwaka wa 1615-16 kulikuwa na uwindaji wa wachawi katika eneo la asili la Kepler, na mama yake mwenyewe alishtakiwa kuwa mchawi. Hata hivyo, hadi mwaka 1620 kesi hiyo ilikoma na yeye akaachiliwa huru. Alipokuwa akijaribiwa, mwana wake Johannes ndiye aliyemtetea. Mwaka 1618 ulifuatana na Vita vya Miaka 30 vilivyoathiri sana Ujerumani na Austria. Kipindi cha Kepler katika Linz kilikuwa kibaya zaidi, kwa kuwa hatua za Counter-Reformation ziliweka shinikizo juu ya Waprotestanti katika mkoa wa Upper Austria ambao Linz ilikuwa mji mkuu. Kwa kuwa Kepler alikuwa afisa wa mahakama, aliachiliwa kutoka kwa amri iliyowatupa Waprotestanti wote kutoka mkoa huo, lakini hata hivyo aliteswa. Kepler aliandika kitabu chake cha Tabulae Rudolphinae, ambacho kilikuwa na maelezo ya juu ya jinsi ya kuunda nyota. Wakati uasi wa wakulima ulipotokea na Linz ikazingirwa, moto uliharibu nyumba na duka la mchapishaji, na pamoja na hilo sehemu kubwa ya toleo lililochapishwa. Askari-jeshi walikuwa katika nyumba ya Kepler. Aliondoka Linz mwaka wa 1626. Kitabu cha Tabulae Rudolphinae kilichapishwa huko Ulm mwaka wa 1627. Kepler sasa hakuwa na cheo wala mshahara. Alijaribu kupata miadi kutoka mahakama mbalimbali na akarudi Prague katika juhudi ya kupata mshahara ambao alikuwa na deni lake kutoka miaka yake kama Imperial Mathemati.