Glass is often described as a slow-moving liquid, but it is really a solid with a disordered structure.

The longer version

Crystals arrange their atoms in a repeating pattern that extends in every direction. The glassy state lacks that order: atoms are frozen in place but positioned irregularly, more like a liquid snapshot than a tidy grid. Because the atoms cannot rearrange, the material holds its shape like any other solid.

The confusion comes from old panes that are thicker at one edge, which was a consequence of how sheets were originally made rather than slow flow. At everyday temperatures the viscosity is so enormous that any movement would take longer than the age of civilisation. Glass therefore remains rigid.

Where this entry sits

Everyday physics and chemistry hide small wonders in plain sight, from kitchen reactions to the light in the sky. These short facts explain matter, energy, electricity, magnets, sound, and the simple units we use to measure the world. The full list sits on the Science and Physics page, where every entry is listed in order.