How do sound waves travel in space? — PS
When sound travels in air, it takes the form of compressions and rarefactions of that air. Similar compressions and rarefactions occur when sound travels in a liquid or in a solid. But sound can’t travel through space because space is entirely empty. Sound requires a medium in which to travel and space doesn’t contain any such medium. Astronauts talk to each other by radio during space walks. With nothing at all between them, they simply can’t hear one another directly.