Imagine two astronauts working on the outside of a space station. one yells instructions to the other astronaut. why can't they hear each other?

There is an empty space, or sounds must travel through matter to make a sound

giant impact theory - the moon was formed from the collision between earth and another mars-sized body.

colliding planetesimals hypothesis - the moon was formed from the same cloud of material as earth.

capture hypothesis - the moon was locked into orbit by earths gravity as it was passing by it.

accretion hypothesis - the moon was formed from collisions and combining of planetesimals.

i think this is right, if not and you know better let me know.