The old man was given knowlage and it's not the first time. It has happened over and over and no they don't know (yet?).
Knowledge*
I think they already know. Why else would they talk about the fact that that power is dropping? We know Dohee is an empty shell that always leaks the power within her.
What I don't understand is why they are trying to find a new host. If the powers are gradually lost, how would it cause a "detonation" like that old man talked about? It would probably just go back to the earth.
Without the knowledge i think it would degrade everything in librium. Also in the chapters they haven't even discovered the old man without powers or even just dead. They were mainly talking about who is and isn't from earth.
there was a scene that says the "powers are leaking if not transferred"..
this powers they are talking about, could it be that it's the knowledge powers from the old man?
if sooo, did they know that it was already transferred to the girl??? -_-
let me know you're ideas