The Triceratops / Torosaurus debate that was making the media rounds recently got me thinking about long-held theories and concepts that were taught when I was in school that have since changed. Notable examples include the official recognition of the mariner's longstanding tradition of there being a distinct Southern Ocean and the debate over the classification of Pluto. I was still in school during the breakup of the Soviet Union, the reunification of Germany, and the end of the Cold War, or else I would include that as well. So what are some significant examples of things you were taught that have changed since you've left school? If you're still in school you can participate too, though we might get angry at you for making us feel old.