[eridius]

Does the expansion of the universe mean that galaxies that are too far away from us are seemingly moving faster than the speed of light, and this is why we can't see any galaxies past a given point (because that's where they "accelerate" faster than light)?

[roywiggins]

A lot of the visible universe actually appears to be receding faster than the speed of light:

https://phys.org/news/2015-10-galaxies-faster.html

It's because the space inbetween is getting bigger. But light keeps moving towards us from those galaxies, so we see those photons eventually anyway. You can still hear things that are going above the speed of sound, as long as they're headed away from you- if they're headed toward you, you'll not hear them (probably?). But the waves they throw off will expand behind them just fine.

[acqq]

> if they're headed toward you, you'll not hear them (probably?)

Actually, you would not have much time to hear, but what you would hear (among the other effects) would be the sound “in reverse”(!)

https://physics.stackexchange.com/questions/14880/hearing-a-...

[rcxdude]

For a practical (if dangerous!) example, see supersonic rounds: if one is shot towards you, you hear the bullet whizzing by before you hear the gunshot.

[LgWoodenBadger]

Well, a supersonic round wouldn't whizz until it drops down to subsonic speeds.

You'd hear the crack of the round then the crack from the original shot.