|Johannes Kepler 1571-1630
|Born on December 27, 1571 near Württemburg, a sickly child with poor parents, Johannes Kepler
was raised largely by his well-respected grandparent since, as Kepler later put it, his father was "an
immoral, rough and quarrelsome soldier" and his mother not much better. Kepler survived a
confusing childhood and began his adult life with modest ambitions for a calm, complacent
meditative life, little aware of the gifts that lay buried within his brilliant mind. He survived in a
tumultuous time when religion and superstition could overpower science.
His own mother was tried for witchcraft during 1615-16, and her defense at trial was conducted by
none other than her son, resulting in her being set free, but not until 1620. There are few examples of
human resilience that rival Kepler's life. In 1584, Kepler entered the Protestant seminary at Adelberg,
and in 1589 he began his university education at the Protestant university of Tübingen where he
studied theology and passed the M.A. examination in 1591, and continued his studies as a graduate
student. His mathematics teacher was Michael Maestlin, one of the earliest astronomers to subscribe
to the heliocentric theory of Copernicus.
He taught only the Ptolemaic system, but in private time acquainted his students with the technical
details of the Copernican system. Kepler accepted an appointment as professor of mathematics at the
Protestant seminary in Graz, Styria in 1594 where he was also appointed district mathematician and
calendar maker, and he taught arithmetic, geometry,Virgil and rhetoric. In 1597, Kepler married
Barbara Müller and published his first important work, 'The Cosmographic Mystery', about the
distances of the planets from the sun.
He stayed in Graz until 1600, when all Protestants were forced to convert to Catholicism or leave the
province. During the period in Graz, the Keplers had three children. In 1600, Kepler was invited to
Prague to become Tycho Brahe's assistant and calculate new orbits for the planets, and upon
Tycho's death was named his successor as Imperial Mathematician, the most prestigious appointment
in mathematics in Europe. He occupied this post until 1612 when Emperor Rudolph II was deposed.
Kepler published a number of important books in Prague: In 1604, 'Astronomia pars Optica',
containing modern explanations of the eye, earned him the title of "founder of modern optics." De
Stella Nova on the new star appeared in 1604, and then 'Astronomia Nova' which contained his first
In 1610, Kepler heard and read about Galileo's discoveries with the spyglass and composed a long
letter of support. Later that year he published his observations in 'Narratio de Observatis Quatuor
Jovis Satellitibus'. Kepler's wife Barbara died in 1612 and Kepler accepted the position of
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 a work on chronology and the year of Jesus's birth in both German and
Latin: 'De Vero Anno quo Aeternus Dei Filius Humanam Naturam in Utero Benedictae Virginis
Mariae Assumpsit', a work in which Kepler demonstrated that the Christian calendar was in error by
five years. This was followed by 'Epitome Astronomiae Copernicanae' between 1617 and 1621, an
introduction to heliocentric astronomy, and in 1619 'Harmonice Mundi', where he derives the
heliocentric distances of the planets and their periods from considerations of musical harmony. The
Third Law published is his 'Harmonices Mundi': The squares of the periodic times are to each other
as the cubes of the mean distances. It was this law, not an apple, that lead Newton to his law of he
founder of celestial mechanics. Kepler also published numerous smaller works.
1618 marked the beginning of the Thirty Years War, making his position in Linz precarious even
though as a court official he was exempted from a decree that banished all Protestants. Kepler
published the seven-volume 'Epitome Astronomiae' in 1621, and was having his 'Tabulae
Rudolphinae' printed when Linz was besieged as peasant rebellion broke out and the printer's house,
shop and much of his new work was destroyed. Soldiers were garrisoned in Kepler's house. He and
his family left Linz in 1626. The 'Tabulae Rudolphinae' were published in 1627.
Kepler's family was Lutheran and he adhered to the Augsburg Confession. However, he did not
adhere to the Lutheran position on "the real presence" and refused to sign the Formula of Concord.
Because of his refusal, he was excluded from the sacrament in the Lutheran church. This, and his
refusal to convert to Catholicism, left him alienated by both the Lutherans and the Catholics. Kepler
now had no position and no salary. He tried to obtain appointments from various courts and returned
to Prague in an effort to collect salary that was owed him from his years as Imperial Mathematician
from the imperial treasury.
He died in Regensburg in 1630 while on a journey to collect a debt. Kepler was constantly in a state
of money worries and forced relocation. Yet through it all, he managed to be first to explain that the
tides are caused by the Moon, first to suggest that the Sun rotates about its axis, first to derive the
now universally accepted birth year of Christ, first to coin the word "satellite," first to explain the
principles of how a telescope works, first to investigate the formation of pictures with a pin hole
camera, first to explain the process of vision by refraction within the eye, first to formulate eyeglass
design for nearsightedness and farsightedness, first to explain the use of both eyes for depth
perception, and first to correctly explain planetary motion.