I suppose you recognize, by title, the situation I am referring to. I don't know if physics people get it as often as math people. The situation of course is that I tell somebody that I am studying math, and if I mention some specifics, like mention Topology or Algebra, (which I have to sort of explain is not "college algebra"), or whatever. Then comes the question "So what's this used for in..you know, real life?" As I see it there are two extremes to answer this question: a) A speech or possible tirade about how this question is not really relevant. Possible comparison of science to art, i.e. "Well, what's the practical application of music?" Trying, perhaps in vain to explain how mathematics doesn't always seek applications but that they often find their uses later, then tell a story about number theory and cryptography. Another variant is that for me, I've studied mathematics for the joy of it and because I think the thinking skills I learned can be applied to anything. b) Just say some stuff I heard about what people might be using this for. "Topological data analysis!" "Cryptography" (again). "Something in physics!"