But from either world, at any given time, you can see varying portions of that lighted half – or various phases of the Earth or moon. The phases are always the reverse of …
Through the 1/r law, it was concluded that for the sound intensity or pressure is directly proportional to distance or radius. That is,
p = k/r
where k is the proportionality constant. If the distance of a sound wave is quadrupled then, the intensity of the sound is decreased to 1/4 of its original value.
#1 and #3 are correct.
#3 is slightly goofy.
The problem is not that there's no air to vibrate your eardrum.
The problem with no air is that there's nothing to ever bring the sound
to your head, even if you're only a foot away from the source. There
are just NO SOUND WAVES going on at all.