It seems to happen in an instant. One second, you're holding a glass of water. The next, it's slipping out of your hand, there's a shattering sound, and suddenly the glass is in a million little pieces all over the floor.
Cleaning up broken glass is no fun. But watching glass shatter in slow motion, the fractures spreading and separating pieces that fly apart, well, that's fun. Check it out:
On a molecular level, when glass shatters the bonds that keep the atoms together are stretching and breaking apart. At least that's what scientists have long thought happened when brittle substances like glass break.
But looking really close at breaking glass - we're talking nanoscale close - scientists saw that glass actually breaks similarly to ductile materials like metal. Instead of stress breaking atomic bonds apart all at once, tiny empty spaces open up ahead of the tip of the crack, making a path of weakness the crack will follow through the glass.
What causes that stress can be physical force, like what happens when a water glass hits the floor. Or it can be sound. Watch a wine glass go to pieces in slow motion with just the power of sound waves:
What's happening here? The wine glass is being bombarded by sound waves at its resonant frequency, the frequency at which its molecules bop around next to each other. If the sound is loud enough and lasts long enough, it'll make the molecules in the glass move around so much they break apart, and the wine glass shatters.
Even when the cause is less melodic, like a ball hitting a sheet of glass, watching cracks spread through glass in super slow motion is pretty amazing:
