Widely considered the first sci-fi book, Somnium was written by astronomer Johannes Kepler around 1608 and was only published in 1634, after his death.
I first heard the claim that the book was used in his mother's witchcraft trial in Astronomy class, and this claim is repeated by APS News:
Kepler also tried his hand at more fanciful writing, penning an allegory called Somnium (The Dream) in 1611 — arguably the earliest work of science fiction, since it centered on a trip to the moon and speculated about what astronomy would be like if conducted on another planet.
Many years later, Somnium would be used as evidence in his mother’s 14-month imprisonment and trial for witchcraft; it described a woman who summons a demon for help in mixing potions. (He revised the work after her acquittal to make the allegorical aspects crystal clear for the too-literal minded.)
Is this true?
One blog I found states that "[t]he records of Katharina Kepler’s trial for witchcraft are still extant and I can state with confidence that Somnium was not only not used as evidence in the trial but was in fact never even mentioned", but never gives evidence from the trial, instead only referencing something Kepler wrote that only vaguely mentions his mother's trial. Considering the stigma of witchcraft allegations, it seems at least probable to me he wouldn't want to talk about it, especially if his book really did have that much of an effect. On the other hand, I'm still not inclined to believe it actually happened either, because Somnium is still a fictional book.