if space contains space dust, wouldn't the space dust be a medium for sound to travel?
Sound is vibrations travelling through air as pressure differences. Think of it as a high and low pressure wave following eachother rapidly.
Since space dust would not be able to have high pressure and low pressure, it couldnt be a medium for sound as we know it to travel.
Imagine a lot of dust on a speaker in space, the very first out push of the speaker drum would send all of the dust off of it, making it impossible to send out any more dust. Also the dust that began travelling would scatter as it hit dust in its path, making complete chaos of the original pulse that started.
Sound can actually transmit through any medium, not just air.
I think a more direct explanation is that, in order for sound to travel through the medium, the medium must be dense enough for the particles to transmit a signal, let alone a coherent one.
The dust particles in a vacuum simply don't bang into each other in any fashion that supports any kind of propogated wave.
It's not that the medium needs to be dense enough. It must be continuous.
For practical purposes, that's the same thing.
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