haha, i learned about that in chemistry class a while ago
something about how the thing carbonates it as you open it giving it a better taste like it was right from the barrel or something
like the old bottles had one and the bottom and the bubbles floated to the top and if you put them in water right side up, they will flip over because of the carbonation on the bottom...
nowadays it is a little ball and spins and it carbonates and gets the whole drink more effectively instead of staying at the bottom and if you put that bottle in the water right side up, it will stay like that because the ball floats inside the can
...yea, thats all i learned in that class