A pebble from the lawnmower that flies against a window. A drink set down too heavily on your glass-topped coffee table. A favorite vase tipped over by your curious cat: These are the types of ...

When a rock hits a side window, the glass often explodes into a shower of tiny cubes, yet the same impact on a windshield usually leaves a spiderweb of cracks that stubbornly hold together. That ...