Has anyone compiled a list of disasters caused by errors in basic math? I don't mean things like the vibration-induced collapse of the Tacomah Narrows Bridge; that involved a fairly sophisticated mistake and a lack of imagination. I mean things like the Hubble Telescope debacle, which I gather in part stemmed from a failure to keep track of units and do necessary conversions. I'm asking because on their final exams, many of my students changed 3^n + (-2)^n to 3^n - 2^n. Next time I teach the course, I plan to explicitly remind them about this common mistake (and to exhort them not to commit it), but even more than that, I'd like to tell them about some memorably terrible thing that happened as a result of somebody somewhere neglecting to use parentheses where they were needed, or misusing them in some fashion. And even more, I'd like to see a compendium of such adverse outcomes, so that any time I want to warn the students away from a particular kind of mistake, I can say something like "If you make this mistake on my exam, you might lose points. And if you make this mistake after you graduate, you might kill hundreds of people." (I don't know if crosses-along-highways are a universal thing, so I'll pause to explain that here in the U.S. they signify places along a roadway where a fatal accident occurred.) Jim Propp