Today we celebrate the birthday of one of the great names in mathematics, Norwegian Sophus Lie (17 Dec 1842 – 18 Feb 1899). Lie made fundamental contributions to the theories of algebraic invariants, continuous groups of transformations and differential equations. Two concepts, Lie groups and Lie algebras, have been named after him.
Beyond being a great mathematician, Lie was, for a short while, also mistakenly considered to be a great spy. He was in Paris during the outbreak of the 1870 French-German war, and decided to leave France for Italy. Before he made it to the Italian border, however, the French arrested him as a German spy. Reason being, they found his mathematics notes, and thought these were secret, coded messages.
It was only after the French mathematician, Gaston Darboux, intervened and confirmed that the notes was in fact legitimate mathematics, that Lie was released.
Based on this experience, Lie decided that perhaps it was safer to return home and continue his work in the Norwegian town of Christiania, where he had originally studied mathematics.
The moral of the story, I guess, is that if you plan on travelling through a war zone with your math notes, keep them plain and simple, or keep them very well hidden!