A 16 oz drinking glass half full of water shatters without any apparent help. The result is a mound of finely ground glass arranged neatly in a circle equal to the original circumference of the bottom of the drinking glass. Can physics explain how this happened? (No physics background here.) Note: While I've heard that sound waves can shatter glass, wouldn't one suppose the glass would move about in random directions and break apart into various sizes. Is there some laboratory experiment that could shatter a drinking glass where the glass would be reduced to this fine mesh and also be contained within its original circumference?