
Oddlet: Johannes Kepler · 1 min read
Oct 26, 2026
Fiolxhilde
Johannes Kepler wrote a short story about a witch who sends her son to the Moon; years after the manuscript leaked, his own mother was on trial as a witch.
Johannes Kepler measured the heavens. His three laws of planetary motion, published in 1609 and 1619, hold today. He also, around 1608, wrote a short story for fun.
In the story, an Icelandic boy named Duracotus travels to the Moon with his herb-woman mother, Fiolxhilde, who summons a lunar daemon to carry them across the ether.
A manuscript leaked around Württemberg in 1611, possibly via a barber. In Württemberg, an herb-woman with an astronomer son was not hard to find.
Katharina Kepler, seventy-four, refused all forty-nine charges (turning into a cat, slipping under doors, riding a calf to death) from the stone floor she was chained to for fourteen months. Her son, from Linz, wrote a 128-page legal brief and spent over 900 gulden, two years of Imperial Mathematician's salary, keeping her alive. She was acquitted in 1621 and died six months later.
Kepler spent the rest of his life burying the Somnium under 223 explanatory footnotes, more annotation than text, insisting the daemon was really an allegory for the scientific method.
He never published it.
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- Britannica — Johannes Kepler — Standard biographical overview: birth/death, three laws, Tycho succession, Imperial Mathematician tenure.
- Stanford Encyclopedia of Philosophy — Kepler — Scholarly biography covering Tübingen education, Mysterium Cosmographicum (1596), Astronomia Nova (1609), Harmonice Mundi (1619), wives, and successful defense of his mother.
- American Physical Society — 'August 1620: Kepler's Mother Imprisoned for Witchcraft' — Details of the trial: Ursula Reinbold accusation, 14-month imprisonment beginning August 7, 1620, October 1621 acquittal by the Duke of Württemberg.
- Wikipedia — Katharina Kepler — Specific dates: arrest August 7, 1620; 405 days pretrial detention; territio verbalis; acquittal 1621; death April 13, 1622; over 900 guilders defense cost.
- Wikipedia — Somnium (novel) — Composition 1608/1609; posthumous 1634 publication by Ludwig Kepler; plot with Duracotus, Fiolxhilde, and the daemon of Levania; connection to mother's trial.
- Smithsonian Magazine — 'Johannes Kepler Defended His Mother in a Witchcraft Trial'

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