Why You Can’t Hear Sound in Space?
For any sounds to reach your ear, it would need a medium (fluid, solid) to propagate. For example, when your friend calls out your name, her vocal folds vibrate and make the sound of your name ‘Tammy’. This vibration traverses through the air, into your ear by vibrating all the air molecules in between you and your friend. When it reaches your ear, the mechanical vibrations in your middle ear is sensed by your hair cells in your cochlea, which in turn sends signals to your brain and helps it to interpret the sound.
The space is almost a vacuum, as all the matters in the universe are separated by a very huge distance. So the distribution of air molecules is of insignificant amount–the density is negligible. When your friend calls you out in the space (hypothetically assuming that you are superheroes who can survive vacuum), there won’t be any air molecules to help traverse her voice–the vibration–to reach your ears. This is the reason why you can’t hear sound in space.
But you can talk to each other if you have a space suit and the right equipment in space to convert the sound into an electromagnetic wave and vice versa. That equipment is called as a radio :) Unlike the mechanical sound waves, the electromagnetic waves can travel through vacuum. So if your friend calls your name in her radio, then her voice will be converted into electromagnetic waves and then it will travel through the vacuum to be received by your radio to be converted into sound again.
This post was first published on November 8, 2014.