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Johannes Kepler: Astronomy and Witchery


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Johannes Kepler, the discoverer of the laws of planetary motion, was born 1571 in the town of Weil der Stadt, Germany; he received a master’s degree from the University of Tubingen in 1588. The great Polish astronomer Copernicus had, in 1533, proposed that the planets revolved in predictable cycles around the sun rather than the earth. For many Christian prelates of the day, this amounted to heresy; after all, the Old Testament tells us that Joshua defeated the Amorites by God’s intervention, halting the sun in its path and extending the daylight. As a student, Kepler became convinced of Copernicus’ heliocentric theory but he remained a steadfast Lutheran to the end.


Leaving Tubingen, Kepler became for several years a professor at the Academy of Graz where he wrote his first book on astronomy. Although his theories turned out to be completely incorrect he attracted the attention of Tycho Brahe, the greatest astronomer of the day, who recruited him as his assistant at his observatory in Prague. Upon Tycho’s death in 1600 Kepler was appointed Imperial Mathematician by the Holy Roman Emperor. He held the position for the rest of his life.

Tycho, a careful and accurate observer, was the last significant astronomer before the invention of the telescope. Relying on his records, Kepler believed that he would determine which theory of planetary motion was correct: the heliocentric theory of Copernicus, the ancient geocentric theory of Ptolemy, or a third advanced by Tycho. However after years of calculations he found, to his dismay, that his mentor’s observations were inconsistent with any of these theories. Tycho and all the classical astronomers assumed that planetary orbits consisted of circles, or combinations of circles. Kepler discovered- and would prove- that planetary orbits were not circular but elliptical; it was a huge scientific breakthrough. He exulted:

I give myself up to divine ecstasy… My book is written. It will be read either by my contemporaries or by posterity- I care not which. It may well a hundred years for a reader, as God waited 6,000 for someone to understand his work.

Kepler went on to provide a complete and correct description of the motions of the planets around the sun, solving many of the basic problems of astronomy that had baffled Copernicus and Galileo. Though unable to prove it- lacking future methods- he was the first to suggest that planetary motions were controlled by forces emanating from the sun. The challenges were immense; mathematical techniques of his day were primitive and calculators had yet to be invented. Kepler did all the laborious computations by hand. In his great book, Astronomia Nova published in 1609, he formally presented the laws of planetary motion. 

Gutenberg’s printing press had resulted in an enormous rise in literacy and the book (written in Latin) would go on to garner a wide audience, Kepler becoming famous throughout Europe. However, the most difficult challenge awaited him; in 1620, his mother was arrested for witchcraft.


Witchcraft trials were not uncommon throughout the Middle-Ages but the phenomenon became a craze around the time Luther nailed his 95 theses to the cathedral door in 1517. Anonymous accusations flew; the air breathed paranoia. Persecutions continued through and after the Reformation; both Protestants and Catholics staged trials with varying numbers of executions.

Around 50,000 Europeans are estimated to have perished in witchcraft trials between 1500 and 1700 and the most common mode of execution was being burned at the stake, a singularly horrific way to die. Several historians estimate that 75% of the victims were females.

In 1615 Kepler’s 68-year-old mother, Kathalina was accused of witchcraft by neighbors in her home town of Leonberg; they had always considered her 'eccentric'. Her crimes were various; a glazier accused her of poisoning his wife and a 12-year-old girl testified that Kathalina had rendered her finger useless by touching her while the two passed on the street. She was also accused of killing local animals and turning herself into a cat. Kathalina was arrested and her incarceration would last for six years; the final 14 months saw her attached to an iron chain on the floor of her cell.

She would have been shown the instruments of torture – they would screw thumbs with heavy irons, and sometimes the thumb would come completely off, causing excruciating pain. They would pull people up on a rack into the air. And she would be talked to in very threatening terms, all the time with a clear agenda to get her to confess.

-Ulinka Rublack, a professor of early modern history at Cambridge

Kepler dropped everything and moved his family from Linz to Leonberg to take up his mother’s defense. His intervention carried the risk of sharing his mother’s fate if one of the zealous prosecutors judged him complicit. At the trial, Kepler displayed a scientist’s logic, a lawyer’s legerdemain, and consummate courage. Rublack describes his defense as a ’rhetorical masterpiece’:

He was very good at spotting inconsistencies, and at dissecting in a very scientific way the accusations. So he mounted a very pioneering defence.

Image result for A statue of Katharina kepler

The statue of Kathalina in Eltigegn

A broken Kathalina was released in the autumn of 1621 and she died six months later, her four children surviving her. She was 74. Not all of Kepler’s siblings rushed to her side like he did — a sister pleaded hardship, a brother withdrew his support when he began to feel threatened, and another brother joined the prosecution. Kepler died in 1630 in Regensburg, Bavaria. During the turmoil of the Thirty Year’s War, his grave was destroyed; the location of his final resting place remains unknown.

Edited by Childress
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 Not all of Kepler’s siblings rushed to her side like he did — a sister pleaded hardship, a brother withdrew his support when he began to feel threatened, and another brother joined the prosecution. 

I’d like to meet that guy. ;)

Part 1: The Ancient Background:

Burning at the stake- and its variations- is one of those most fearful modes of execution; the practice goes back to ancient Babylonia. It’s also mentioned in the book of Genesis, usually reserved for sexual crimes but that Hebraic custom eventually died out. Diodorus Siculus, a 1st century Greek historian, mentions the so-called Brazen Bull a torture and execution device that was used centuries before:

The bull was said to be made entirely out of bronze, hollow, with a door in one side.. According to legends the Brazen Bull was designed in the form and size of an actual bull and had an acoustic apparatus that converted screams into the sound of a bull. The condemned were locked inside the device, and a fire was set under it, heating the metal until the person inside was roasted to death. -Ancient World Review


Julius Caesar reported that the ancient Celts practiced the burning alive of humans, that being prescribed by Druidic law. The Romans, horrified, stamped out the tradition throughout the empire and there are few reports until the reign of Nero who blamed the famous Fire of Rome in 64AD on the tiny sect of Christians residing in the Rome. He had the victims wrapped in the ‘tunica molesta’ a garment doused in pitch that was lit and raised on poles to illuminate the City streets at night. There was a lull until the 3rd century when we read that Roman jurisprudence declared that army deserters and arsonists were liable to death by fire.

The state reacted similarly to the burgeoning number of Christian converts- without enduring success- and the members of the new faith would grow to command the heights of the government. But the Christians eventually devolved into battling sects, destabilizing the state. Beginning with Constantine the Great in the 4th century the Christians deemed heretics were, in a reversal of fate, now vulnerable to burning and the practice continued into the Byzantine Empire. But compared with late Medieval Europe, the era of Kepler, these auto-da-fés were likely on a small scale.

Edited by Childress
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