Fluid dynamics is always quite interesting...
I’ve experienced the “superheated water” effect in a microwave oven, where water is heated well beyond the boiling point, but it doesn’t form any bubbles, and appears to not be boiling. Break the surface tension and WHOOSH! It flashes to steam and boils violently in an instant!
Mark
Put a stick in the water (I use a clean chopstick) before microwaving. It gives the bubbles something to cling to. Works every time! (got the tip from Alton Brown's "Good Eats" show on the Food Network).
This scared me big time at first because I’d get tired of waiting and remove the cup of water thinking is just won’t boil and go ahead and put in a spoonful of instant coffee and it would go off like a volcano! I then saw it on one of those 20/20 dumb science segments. Thing is the container was super clean and smooth. They said that would happen in a saucepan on the stove, too, but no pan is that smooth. They advised stopping the microwave and stirring the water will jostle it up enough. I find that only cups and glass measuring cups washed in the dishwasher are likely to do that. Looks like anything I wash by hand is not that clean and therefore it boils like crazy.