Space is silent because sound needs a material medium such as air to travel.

The longer version

Sound travels as a pressure wave moving through matter, with molecules bumping into neighbors and passing the vibration along. A vacuum has essentially nothing to carry that motion, so a ringing bell in space would transmit no sound at all, no matter how violently it rang. Explosions there would produce vibration in solid objects but no audible noise.

Astronauts can still talk to each other inside a pressurized cabin because the air inside does the work, and radios carry voices as electromagnetic waves. Space is not completely empty, but the gas between planets is so thin that any wave would be far too faint to hear.

Where this entry sits

The night sky looks calm, yet almost everything up there is moving, burning, or slowly changing. These facts cover planets, stars, the Moon, gravity, black holes, comets, and the story of how people began exploring beyond Earth. The full list sits on the Space and Sky page, where every entry is listed in order.