Sound cannot travel through a vacuum because there are no particles to carry the vibration.

The longer version

A vacuum contains no matter to compress and relax, so there is nothing to pass a vibration along. Sound is a mechanical wave, meaning it needs a material medium such as air, water or steel. With no particles to nudge one another, the disturbance simply has nowhere to go.

Light behaves differently, because it is an electromagnetic wave that needs no medium at all and crosses empty space freely. That contrast is why fictional scenes of explosions in space would actually be silent. Inside a spacecraft, air carries sound perfectly well, since the cabin is filled with gas.

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.