Everyone knows that light travels quickly and sound travels slowly. Those people who know that light and sound aren't instantaneous, anyway. It's odd, that: I don't really believe in action at a distance because I can't see how it would work, and yet talking to people with no computational/mathematical/scientific bent, action at a distance seems to be the natural assumption.
I guess it leaves more room for their gods.
And it's not that unreasonable an assumption, most of the time. I had proof of its reasonableness this week, when – for the first time I can remember – I was able to experience the relative sluggishness of sound, after almost thirty years on Earth.
I was sitting about 300m, I guessed, from a digging machine. This digging machine was using its scoop to bang a girder into the ground. I'd see the contact, wait almost a second, and only then would I hear the sound.
Weird! I must never have sat an appropriate distance from repetitive construction work before.
Google confirmed my memory from school of the speed of sound at sea level. The US may be notorious for its use of archaic units (and how embarrassing that they should refer to them as "English"), but at least the geeks at Google have the sense to respond to a search for "speed of sound" with "speed of sound at sea level = 340.29 m / s".
When I mentioned my excitement to someone, they said "what about thunder and lightning?" but that seems different because I for one have no idea where the thunder or the lightning are. They're in visible/audible range, but where exactly? And it's not quite as convincing that they're the same event; I couldn't swear to knowing anything about thunder or lightning. Whereas I think I understand the basics of banging one piece of metal against another.