Blogging - kathrynneal

The water in the glass has been cooled down to below freezing point. However, seeing as how it's been done carefully, in a very clean glass, it's had no seed for any ice crystals to form, so it continues to jostle around in the liquid state (albeit very unwillingly). Add the ice-cube, suddenly you have a seed, and because the water it already well below freezing point, it all latches straight onto the growing ice crystal. All in all, it is actually very similar in concept to Vonnegut's Ice-9, the big difference being is that there isn't actually a polymorph of ice that is stable at 45° (?) and 1 atm, because otherwise essentially all terrestial ice would be of that form (As it would be thermodynamically favourable to Ice Ih).