Academic-turned-teacher (but still doing research as a hobby), interested in mathematical logic - specifically, computability theory and reverse mathematics, set theory, and abstract model theory. I`m also interested in other Nifty Things, in mathematics and elsewhere. Since the SE system only allows temporary bounties, I am here informally "perma-bountying" the following ten questions, each for 1000 points: Geometry and topology: Model theory: Descriptive set theory: Set theory: Computability theory: ©