You may have heard that glass is a liquid, and that it slowly, slowly flows, causing older windows to have thicker bases. But don't believe the myth! Those windows have their bigger bottoms simply due to the glass-making process of the time, which left some panes with non-uniform surfaces. (Also, many old glass items don't even exhibit this feature.) As an amorphous solid, glass has a structure that is more rigid and organized than that of a liquid, but less so than a pure solid like a crystal.
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Key Facts In This Video
Although it looks like a solid, pitch is actually a extremely viscous liquid at room temperature. 00:27
Glass is an amorphous solid—its molecules aren't arranged in a typical crystalline structure. 02:42
We can see the shadow of the Earth's liquid outer core by measuring seismic waves from an earthquake on the other side of the world. 04:25