In relation to this question:
Which notes that the hole "produces" sound. The top answer states that:
What you think of as the hard vacuum of outer space could just as well be seen as a very, very, very diffuse, somewhat ionized gas. That gas can support sound waves as long as the wavelength is considerably longer than the mean free path of the atoms on the gas.
I get that there is "stuff" in space, what I don't get is how sound travels it. I learnt in high school that sound was a wave - as an example, you could fix a shoelace at one end and vibrate the other - voila, a wave forms.
And then sound kind of moves in the same way through, say, air, because of the slight molecular attraction between individual molecules is enough to create a similar waveform.
And then you get to space, and there aren't any molecules nearby to irritate each other, so there's no sound.
If that's the case, why does it matter how long the wavelength is, if there isn't a molecule nearby for the initial molecule to affect, how can sound travel?
I'd understand a little better if the particle a just hit particle b (like a pool ball) and b carried the sound - but that has little to do with waves and wavelengths.
Or is it that the "jet" that is thrown out travels along as a contiguous blob, with a sound wave embedded within it?