Some men have had such a profound impact on the course of human events that they are universally regarded by historians as geniuses. Johann Kepler was one such man.

Astronomer by Candlelight by Gerrit Dou, 1650s

Kepler was born on December 27, 1571 in Weil der Stadt, a small town in the Holy Roman Empire. His family was not well to do—his mother Katharina was the daughter of a formerly rich inn-keeper and his father Heinrich was an immoral mercenary who often left for long periods of time. As a result, Kepler lived with his grandparents and unhappy mother at the inn, where he served as a busboy when he wasn’t in school. He did not have a happy childhood.

But he was bright, and in those days the nobility would sponsor bright young men for further education, believing an investment in them would be paid back with loyalty later. As a talented young student Kepler was noticed by the Duke of Wurttemberg and brought to the University of Tubingen at the age of 18 in the hopes he would use his gifts to become a professor, a minister, or a statesman. For his part, Kepler wanted to be a minister.

At the university he studied Greek, Hebrew, arithmetic, geometry, astronomy, and music under the world famous astronomer Michael Mastlin, and it was this more than anything else which was to shape the course of his life. Kepler quickly proved to be a star pupil, and it wasn’t long until Mastlin privately introduced him to the heliocentric idea of astronomy being guessed at by Copernicus. Kepler accepted it almost at once, as it awoke in him the idea that God had deliberately put the brightest and most glorious thing in the center of the solar system, having organized the universe according to a grand plan. It would be an idea he would firmly hold to for the rest of his life.

In Graz

By his second year at the school Kepler had earned his M.A. and was well on his way to becoming a minister of the gospel, but as he studied he fell out of orthodox Lutheranism (as defined by the Augsburg Confession) and into Reformed theology. Since there was no way a Lutheran school would let a Calvinist become a minister, Mastlin (a former Lutheran minister himself) suggested Kepler take up teaching mathematics at the high school in Graz Austria. He did.

At the Protestant school Kepler taught rhetoric, history, ethics, and land surveying in addition to spending his private time figuring out why the planets orbited the way they did. Two years after accepting the post (in 1596) Kepler wrote his famous book, Mysterium Cosmographicum which laid out a case for God creating a heliocentric solar system using Euclidian shapes and forms. It was an innovative idea and an instant success, and although it was totally wrong, it had the effect of putting God into the field of astronomy. Kepler would later write to Mastlin, “I wanted to become a theologian; for a long time I was unhappy. Now, behold, God is praised by my work, even in astronomy.” 1Personal Letter to Michael Maestlin (3 Oct 1595). Johannes Kepler Gesammelte Werke (1937- ), Vol. 13, letter 23, l. 256-7, p. 40.

The next year he married 23 year old Barbara Muller and began his family life, but it wasn’t the most tranquil of times. Kepler had made a habit of argumentation and debate at the university, and while it’s a good strategy for discovering the weakness in a scientific theory, it’s not a prudent plan for a peaceful marriage. Worse, the couple’s first two children died in infancy (although the next three survived), and the two never really developed a knack for living together on his poor income.

In Prague

Johann Kepler

Kepler wouldn’t spend very long teaching however, as the unrest that was sweeping over Europe would soon sweep him out of Ginz. In 1597 the Catholic archduke Ferdinand banished all Protestants from his country, emptying the school where Kepler taught and effectively ending his job. But when God closes one door He opens another, and in 1600 Imperial astronomer and Danish nobleman Tycho Brahe wrote to Kepler’s old mentor Mastlin asking him to for an assistant to help sort out his extensive observational data. Brahe had collected copious amounts of notes regarding the orbit of the planets, and being weak in math he required someone strong in it to help him work out the equations they represented. Mastlin recommended Kepler; the timing was providential.

Kepler set off straight away, having long desired to use Brahe’s world class equipment to prove his own theory for some time, but upon meeting him the two quarreled and Kepler stormed off. He didn’t get far however—remembering how his family wasn’t going to be welcome in Gintz for much longer and being very poor, he swallowed his pride and apologized, begging for the assistant’s job. Brahe not only gave it, but supplied his salary and quickly put him to work calculating the orbit of Mars.
After four months had passed Kepler was settled, and it was time to travel back to Gintz to fetch his family. It was none-too-soon too, upon arriving he found they’d just been banished from Graz.

Once back it didn’t take long before Kepler was working diligently for his new (abrasive) patron. Together they were a formidable team, and the two began to calculate the position of the stars and planets in a catalogue called the Rudolphine Tables which would predict their motions in the future. But things weren’t to last. Less than a year into their work Brahe became deathly ill, and with his staff leaving, he asked the emperor to make Kepler the imperial observer in his place upon his passing. Emperor Rudolph granted the request, and Kepler was put in charge of the imperial observatory.

Tycho Brahe

Faithful to the promise he made to Brahe, Kepler not only continued to compute the orbit of Mars over the next few years, but he worked on the orbit of the Earth, published the first two of his laws of planetary motion on elliptical orbits and equal areas, and postulated the theory of the tides as a function of the nearness of the moon. Because of the work done at this time he came to be widely regarded as the father of celestial mechanics, father of the scientific method, and thanks to his work Astronomia Pars Optica published in 1604, the father of modern optics.

But even though he was productive and successful, a shadow was falling over his future at Prague. By 1604 the kingdom was nearly bankrupt, and the Emperor could no longer afford to pay Kepler. In order to make ends meet he turned to writing horoscopes for the nobility (which he hated) to supplement his income as necessary. But even this was soon to come to an end.

In Linz

In 1611 providence dealt harshly with him. Tragedy struck when his beloved seven year old son died of pox, and shortly thereafter his wife of 15 years died of typhus. Then, in June the Hapsburgs persuaded a very Catholic Matthias, brother to Emperor Rudolf, to march on the city and take the crown for himself. Kepler stayed with Rudolph until the end, and the gesture so touched Matthias that he made Kepler the imperial mathematician in Linz, Austria. Kepler and the surviving children moved again, but better times were not ahead. No sooner had he settled down in Austria than he was declared to be a heretic and excommunicated because he’d criticized of a local preacher by the name of Daniel Hitzler.

In 1613 Kepler remarried, this time choosing a poor orphan girl 17 years his junior, and of their seven children only one survived to adulthood. And to top it all off in 1615 Kepler’s mother was accused of witchcraft. He was forced to go at once to advocate on her behalf for over a year until she was free. (He got her off on a technicality that she wasn’t tortured according to proper procedure).

It was at this time that he published his third law of planetary orbits as part of the formula which would tie all disciplines together. His famous statement “O God, I am thinking Thy thoughts after Thee,” was more true now than ever.

But life at Linz wasn’t all bad. Susanna Reutlinger proved to be a much better wife for him than Barbara for the simple reason that she genuinely loved him, and his second marriage was much happier than his first. He also resumed work on the book he’d started many years earlier at Gantz on the harmony of astronomy, music, geometry, and astrology, trying to develop the overarching explanation for everything. It was at this time that he published his third law of planetary orbits as part of the formula which would tie all disciplines together. His famous statement “O God, I am thinking Thy thoughts after Thee,”2Personal letter to Johannes Georg Herwart von Hohenburg (1599). The above is a shortened form of the full quote, “These norms are within the grasp of the human mind. God wanted us to recognize them by creating us in His image so that we could share in His own thoughts… and, if piety allows us to say so, our understanding is in this respect of the same kind as the divine.” was more true now than ever.

Kepler’s Platonic solid model of the solar system, from Mysterium Cosmographicum (1596)
A plate from Astronomia Pars Optica, illustrating the structure of eyes (1604)

Between teaching mathematics and working on his magnum opus Kepler also wrote the first proof for the newly invented logarithm, and laid the groundwork for integral calculus later picked up by Newton and Leibnitz in his book Stereometria Doliorum Vianiaorum.

In 1626 the Thirty Years War became personal, and Linz was besieged by farmers rebelling against the Bavarian Catholics. He left at once for Ulm, and upon arriving he finally finished the Ruydolfine Tables which would predict the planetary motions more accurate than anything to come for over a century.
In 1627 the emperor received a copy of it and was so pleased that he offered to take care of Kepler and his family for the rest of their lives on the condition he convert to Catholicism. Loyal to God and his conscience, Kepler declined.

Hard pressed for money he went to Regensburg to collect on some debts, but he fell ill on the way and died November 15th, 1630 at the age of 59. It was an ignominious end to such a bright and faithful man.

Portraits of Kepler and his wife, Barbara Müller.

Legacy

Emperor Matthias as Archduke by Lucas van Valckenborch

If you ask a scientist they’ll tell you Kepler is best known for his three laws of planetary motion which proved Copernicus right. If you ask a historian they may tell you he was great because of his groundbreaking work on optics, calculus, telescopes, logarithms, the scientific method, and astronomy which brought science out of speculation and into the realm of observation.

Daniel Hitzler

But if you ask a Christian what Kepler’s lasting impact was he’s likely to tell you it was his contribution to worship. As A.W. Tozer once said, “it’s not what a man does that makes his work secular or sacred, it’s why he does it.”3A.W. Tozer The Pursuit of God, 127 Kepler had wanted to become a priest to proclaim the excellences of God’s attributes, but God had chosen for him to instead proclaim His virtues through creation. As Kepler said, “We do not ask for what useful purpose the birds do sing, for song is their pleasure since they were created for singing. Similarly, we ought not to ask why the human mind troubles to fathom the secrets of the heavens. The diversity of the phenomena of nature is so great and the treasures hidden in the heavens so rich precisely in order that the human mind shall never be lacking in fresh nourishment.” 4Mysterium Cosmographicum. Quote sourced from Carl Sagan, Cosmos (1980, 1985 One cannot read the above without having Proverbs 25:2 come to mind: “It is the glory of God to conceal a thing: but the honour of kings is to search it out.”

From the start of his life to the end of it Kepler’s driving passion was to reveal the glory of God and proclaim His greatness. As he said, “Purposely I break off the dream and the very vast speculation, merely crying out with the royal Psalmist: Great is our Lord and great His virtue and of His wisdom there is no number: praise Him, ye heavens, praise Him, ye sun, moon, and planets, use every sense for perceiving, every tongue for declaring your Creator… to Him be praise, honor, and glory, world without end. Amen.”5J. Kepler, Epitome of Copernican Astronomy and Harmonies of the World, translated by C. Glenn Wallis, Prometeus Books, New York, 1995, Book V, ch. 9, p. 240 and ch. 10, p. 245.

 

Endnotes   [ + ]

1. Personal Letter to Michael Maestlin (3 Oct 1595). Johannes Kepler Gesammelte Werke (1937- ), Vol. 13, letter 23, l. 256-7, p. 40.
2. Personal letter to Johannes Georg Herwart von Hohenburg (1599). The above is a shortened form of the full quote, “These norms are within the grasp of the human mind. God wanted us to recognize them by creating us in His image so that we could share in His own thoughts… and, if piety allows us to say so, our understanding is in this respect of the same kind as the divine.”
3. A.W. Tozer The Pursuit of God, 127
4. Mysterium Cosmographicum. Quote sourced from Carl Sagan, Cosmos (1980, 1985
5. J. Kepler, Epitome of Copernican Astronomy and Harmonies of the World, translated by C. Glenn Wallis, Prometeus Books, New York, 1995, Book V, ch. 9, p. 240 and ch. 10, p. 245.