Template:Are You Sure/January 14

• ... that mathematician Kurt Gödel's first incompleteness theorem states that for any self-consistent recursive axiomatic system powerful enough to describe the arithmetic of the natural numbers (for example Peano arithmetic), there are true propositions about the naturals that cannot be proved from the axioms?

• ... that "Asking for a Friend" is a song by the Rolling Stones?

• ... that mathematicians Hugo Steinhaus, because of his Jewish background, spent the Nazi occupation of Poland in hiding; and that he taught clandestine classes, higher education being forbidden for Poles under the German occupation?