People wonder whether a tree falling in the woods actually makes a sound if nobody's there to hear it, but nobody ever asks about whether water being poured down a seemingly bottomless well makes a sound- and how long it takes to do so.
However, Unecht Erfunden wondered about this watery issue when he visited Nürnberg Castle, so he poured a pitcher of water down a medieval well 50 meters long and discovered it takes a long time to echo back.
-Via Laughing Squid