"You know of echoes, right? You know they aren't always caused by a creature that repeats whatever you say. The time between when you call out and when you hear the echo is the time it takes for the sound you made to hit something, like a solid rock wall, and travel back to you. In fact, if you find a large enough room without any tapestries, say something the size of the Great Hall, then you'll get a pretty good echo in there. If you need more proof, go watch a thunderstorm and tell me why when lightning strikes at a distance the thunder doesn't come right away."
First you prove that it happens... and then once you got their interest, you tell them why and how it happens. And pretty soon, DADA turns into The Engineer's Guide to Crippling Your Opponents.
First you prove that it happens... and then once you got their interest, you tell them why and how it happens. And pretty soon, DADA turns into The Engineer's Guide to Crippling Your Opponents.