* Sound waves are vibrations: Sound is created by vibrations that travel through a medium, causing molecules to bump into each other.
* Vacuum lacks a medium: A vacuum, by definition, is an area devoid of matter. There are no molecules or particles present for the sound waves to vibrate.
* No molecules, no vibrations: Without any molecules to vibrate, the sound wave cannot propagate. It simply dies out.
Think of it this way: Imagine trying to start a chain reaction by pushing one domino over, but there are no other dominos set up behind it. The first domino falls, but the chain reaction stops there. Sound waves in a vacuum are similar – they start, but there's nothing to carry the vibration forward.
