Do others have bits of 'simple' (or, indeed, complex, but the simple has a bigger 'wow' factor, I reckon) Physics that make you go 'wow', 'huh?' and 'I dunno!' all in one fell swoop? I recall a very easy demo in an early QM lecture - take two polarising polarizing filters arranged at 90 degrees to each other (say, on an overhead projector so you can see it well). Lo and behold no light. That makes sense. Then add another filter on top of those two at 45 degrees. Lo and behold - light. That's completely crazy really. The mathematics works (and is very simple) BUT there wasn't light, and then there is. As my lecturer said (to paraphrase) 'If anyone can explain that in physical terms they'll become rather famous'. Simple, but a touch wierd.