Rouven Jahnke — NotesInformal mathematical notes by Rouven Jahnke.https://rouvenjahnke.com/en-usA first look at the twenty-seven lines on a cubic surfacehttps://rouvenjahnke.com/notes/2026-04-twentyseven-lines/https://rouvenjahnke.com/notes/2026-04-twentyseven-lines/Working notes on the classical theorem that every smooth cubic surface in three-dimensional projective space contains exactly twenty-seven lines.Wed, 15 Apr 2026 00:00:00 GMT