Johannes Kepler

Johannes Kepler

“Truth is the daughter of time, and I feel no shame in being her midwife.” – Johannes Kepler.

Johannes Kepler Biography

Johannes Kepler was born on 27 December 1571 in Well der Stadt, a small town in what is now the Stuttgart region of Germany. He was the fourth child of Heinrich Kepler, a mercenary who left the family when Johannes was only five and is thought to have died in the eighty years war. His mother, Katharina, was an innkeeper’s daughter. She did her best to allow Johannes to experience the wonders of nature, and it was probably because of this that he developed a love for astronomy. It was she who took him to a high place in order for him to see the great comet of 1577 better and it was probably she that called him outside in 1580, when he was nine, to look at the lunar eclipse.

In 1589, after leaving grammar school, Kepler attended the University of Tübingen, and proved himself to be a skillful mathematician. Under Michael Maestlin, the university’s professor of mathematics, he learned about planetary motion and became a fan of the Copernican system which put the Sun, rather than the Earth at the center of the universe.

Kepler had wanted to become a minister, having studied both philosophy and theology whilst at university, and having attended seminary at Maulbronn before that. However, he was recommended as a teacher of mathematics and astronomy at a school in Graz, a position which he took up at the age of 23 in April 1594. Whilst teaching at Graz, Kepler claimed to have an epiphany on 19 July 1595 in which he believed that he was shown God’s geometrical plan for the universe. His experiments led him to publish a book called Mysterium Cosmographicum in 1596. A second edition of which was published in 1621 included all of his observations and corrections since the first edition was published some quarter of a century earlier.

The year before he published Mysterium Cosmographicum, Johannes Kepler was introduced to Barbara Müller, a 23-year-old, twice-widowed mother of one, and they began courting. The couple was married on 27 April 1597. They had two children who died in infancy, but three more children would follow, a daughter called Susanna and two sons, Friedrich and Ludwig.

Following the publication of Mysterium Cosmographicum, Kepler formulated grand plans to expand on the work, by publishing four more books dealing with the sun, stars, planets and their motions, the physical nature of the planets and the effects of the heavens on the earth. In order to help him with his work, he began correspondence with a number of eminent astronomers, to whom he had previously sent copies of his book. One such person was Tycho Brahe, who was particularly critical of the use, in Kepler’s work, of the inaccurate data supplied by Copernicus. Never the less, the two started regular correspondence. Eventually, and amidst, growing religious tension in Graz which was threatening his employment, Kepler accepted an invitation from Tycho to visit him in Prague.

Kepler arrived in Benátky nad Jizerou, about 35km outside of Prague, where Tycho Brahe was building a new observatory, on 4 February 1600. He met Tycho and his assistants and stayed for the next couple of months as a guest, and as Tycho began to trust Kepler, he allowed him more and more access to his data. Following an argument, however, over negotiations for a more formal arrangement of employment with Tycho, Kepler left and headed to Prague. The pair soon came to an arrangement though and Kepler returned to Graz to collect his family. Political and religious tensions in Graz meant that he could not return immediately to Brahe, but when he refused to convert to Catholicism he was banished, and he and his family headed to Prague, where from 1601, he was supported by Tycho Brahe but on 24 October 1601, Tycho died unexpectedly. Kepler was appointed his successor as the imperial mathematician with the responsibility to complete Brahe’s unfinished work.

As the imperial mathematician, Kepler’s primary responsibility to Emperor Rudolph II was to provide astrological advice. Kepler had been providing detailed horoscopes to friends and family since his university time, and so this presented no problem for him. The emperor showed an active interest in Kepler’s work and, on paper at least, provided an ample income. However, due to he financial troubles the emperor was experiencing at the time, actually getting hold of enough money to look after his family proved difficult and was causing problems for him at home. However, this was balanced by the fact that his position at court allowed him to practice his Lutheran religion without hindrance and also provided him with access to other scholars, which allowed his astronomical work to progress quite rapidly.

As he also now had unrestricted access to Tycho Brahe’s work, he also made leaps and bounds with his work on optics and actually paused most of his other work during 1603 to work exclusively on the subject. This resulted in a manuscript which he presented to Emperor Rudolph on 1 January 1604. The manuscript was published as Astronomiae Pars Optica (The Optical Part of Astronomy) within which it should be noted that Kepler was the first to correctly describe that images are presented to the human eye upside down before being inverted by the lens for presentation to the retina. The work is now considered to be the foundation of modern optics.

In October of 1604, Kepler began to systematically observe a bright new evening star, a supernova, which led to him to conduct more research into the phenomenon. The research resulted in the publication of Astronomia nova, within which are published Kepler’s first two laws of planetary motion.

Kepler then switched his focus back to the Rudolphine Tables, which was the unfinished work he took over from Tycho Brahe. The tables included specific predictions of planet and star positions, but the work would continue for several more years before it was completed.

In 1610, Kepler was contacted by Galileo Galilei who told him of his observations of four new satellites orbiting Jupiter, essentially to seek confirmation of his observations. This confirmation came enthusiastically from Kepler as he realized the significance of not only Galileo’s observations but the means by which they had been achieved. Through the use of a relatively new device called a telescope.

The following year Kepler published a description of the symmetry of snowflakes and extended the discussion to include a statement about the most efficient way to pack spheres, something which came to be known as the Kepler conjecture. However, 1611 would mark another significant turn in Kepler’s life. Emperor Rudolph’s health was failing and after he was forced to abdicate by his brother Matthias as King of Bohemia, it became apparent that Kepler’s days at court were numbered. During the same time, his wife Barbara became ill with Hungarian spotted fever and all three of his children contracted smallpox. Friedrich, his six year old son died, and soon afterwards so did Barbara. Kepler had been offered a post by the University of Padua as mathematics professor to replace Galileo, but he wanted to keep his family in Germany. He had arranged for a move to Linz as a teacher and mathematician, but delayed his departure following the deaths of his wife and son. On the death of the emperor in 1612, Matthias actually re-affirmed Kepler’s position at court, but allowed him to move to Linz.

Whilst in Linz he published a formal and systematic work on the year of Christ’s birth and also wrote a similarly detailed treatise on how to measure the volume of containers. The first was published in 1613 and the latter in 1615. In the same year as the publication of the work on the date of Christ’s birth which was called De Vero Anno, he married a 24-year-old woman called Susanna Reuttinger. They had six children, although the first three died in childhood. The next three, though, Cordula, Fridmar, and Hildebert survived.

Between 1615 and 1621, Kepler published a three-volume work called Epitome astronomiae Copernicanae (Epitome of Copernican Astronomy), which contained all three of his laws of planetary motion, with the first two being purposefully extended to cover all the planets, the moon and the satellites of Jupiter. This would become his most influential work. He also published astronomical calendars in which he would forecast political events, the weather, and planetary positions. These became very popular and helped him to offset the cost of producing his other work. By 1624 though, the calendars started to cause more trouble than they were worth, partly due to the ambiguity of his predictions. The last of his calendars, published in 1624, was publicly burned.

During this time, Kepler had to turn some of his efforts in another direction when his mother, Katharina, was accused of witchcraft. Kepler devised a successful legal defense and after 14 months in prison, Katharina was released in October 1621.

By 1623, Kepler had finally completed the Rudolphine Tables, but they would not be printed until 1627, at Kepler’s own expense in the city of Ulm, which was where Kepler and his family had moved to following more religious tension, and the besieging of Linz in 1626.

The following years consisted of a lot of travel following the military success of the emperor’s forces. He spent time in the imperial court in Prague as well as in Linz and Ulm. He finally moved to Regensburg in the South East of Germany, but shortly after arriving there he fell ill. Johannes Kepler died on 15 November 1630. He was buried in Regensburg.

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