Johannes Kepler Is Born, 1571

While a college/seminary student, Kepler was introduced to the work of Nicolaus Copernicus who had written that planets orbit the sun rather than the Earth, a revolutionary break from Church dogma and astronomic belief. With his brilliant mathematical skills and astrological acumen, Kepler was invited to become, at the age of twenty-three, professor of mathematics at the Protestant seminary in Graz, Austria. In his spare time he studied astronomy and astrology (considered nearly the same discipline in that era). He took a public stand for the heliocentric Copernican theories in his first published work, in opposition to both Luther’s and the Catholic Church’s belief. So dangerous was his theory considered that he and his first wife, Barbara, wrote to one another in code to minimize the chance of persecution.

Johannes Kepler (1571-1630

Kepler was skilled at ingratiating himself with men who could promote his career, and he received the benefits of several patrons. He also married an heiress, twice widowed, and together they had five children. Kepler corresponded with other prominent astronomers and ran afoul of Tycho Brahe, one of the foremost scientists of his day, a wealthy Danish nobleman-astronomer. They debated Copernican theory and eventually came together at Tycho’s new observatory near Prague, after Kepler fled Graz for refusing to convert to Roman Catholicism. Brahe added Kepler to his growing cadre of assistants, but was careful not to reveal to him all that he had discovered about planetary motion. Upon Tycho’s death that very year, Kepler was appointed Imperial Mathematician and given the task of completing Tycho’s work.

Over the following eleven years Kepler came into his own using Brahe’s notes and his own observations. Kepler was so respected that he was permitted his Lutheran convictions though the emperor’s court was Catholic. His duties included “reading the stars” and giving astrological advice to the Emperor, as he continued serious astronomical calculations and collegial contact with the other mathematicians of Europe. It took him eight years to solve the problem of explaining the unusual Mars orbit. He discovered the planets travelled in ellipses rather than circles, now known as Kepler’s First Law. He figured out that planets further from the sun moved more slowly, Kepler’s second law (1609). In comparing the orbits of two planets he found that “The square of the ratio of the period of two planets is equal to the cube of the ratio of their radius” (Third Law, 1619).

He wrote many other works, some of which still hold up. Kepler’s contributions to astronomy accorded him the title of “Father of Astronomy” by historians. Tubingen would not let him return because his Calvinist beliefs conflicted with strict Lutheranism and eventually he had to move to Linz. During the Thirty Years War, Linz was laid siege to by Catholic armies and he had to move again. Ironically, Kepler became an advisor to the Catholic General Wallenstein but failed to predict Wallenstein’s assassination. Kepler’s gravesite was lost when the Swedish army destroyed Regensburg, where he had died in 1630. It was this great Christian astronomer who is said to have remarked that “I think God’s thoughts after him,” a central tenet of twentieth century Reformed presuppositional apologetics.