MP Board · Class 9 · Science · SoundExplain why two astronauts standing on the Moon cannot hear each other's voice directly without electronic equipment.

Sound is a mechanical wave that strictly requires a material medium (solid, liquid, or gas) to travel, as it propagates through the collision and energy transfer of neighboring particles. The Moon has no atmosphere, meaning there is complete vacuum on its surface. Since there are no air molecules on the Moon to carry sound vibrations from one point to another, sound waves cannot propagate. Thus, astronauts must rely on radio signals (electromagnetic waves) to communicate.