The latest comic from Randall Munroe at xkcd is funny, due to the ignorance about how homeowner’s insurance works. But the concept of shining a blacklight on your bathroom is a new one on me. Do we dare try it? Some people clean their toilets on a regular schedule, while others only clean it when it looks dirty. Urine glows under a UV light, which this page recommends for finding pet stains on a carpet. That seems like a good idea. But they also mention using a blacklight to see how clean your hotel room is …and that can be frightening. There are some things it’s just better to not know.