I recently did a presentation in a secondary school containing - among other things - some encouragement towards studying maths, engineering and the natural sciences. I did a quick walk-through of the Hyatt Regency disaster back in 1981, where a small design change altered the load on critical components, and led to a catastrophe. http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse The example, I think, was ideal for the situation. Easy to understand, but not entirely trivial (it took a few attempts from different pupils before one of them spotted the critical error), and a rather dramatic setting and outcome. Does anyone here have suggestions for similar examples suitable for catching interest and provoking thought in people of this age bracket (13-17)?