https://0x0.st/iAau.pdf Undergrads in Arkansas apparently are not rated for thinking in terms of analogy, so this problem has been judged inappropriate for a class on physics. The other difficulties are that they don't know how to fit data, work with error bars, calculate standard deviations, integrate functions, etc. In this case, adding, subtracting, and function evaluation is too much to ask for, because students (mostly from engineering) expect cookies to be cut in a particular way. Too bad because I was interested to hear what they think about the Nature article, see also: https://media.nature.com/original/magazine-assets/d41586-019-03241-9/d41586-... Anyone here have an opinion about the local extinction data? Or suggestions what to do as a teacher in this situation? --Brad