They walked down to the ex Cold-War nuclear bunker, where the machine was held.
"Still not getting the difference with the parallel Universe thingy..."
"Hmmm... Well, think of it this way. Our reality is a room in a house. Other, alternate, realities are other rooms; but in the same house."
"So what about the Parallel Universe?"
"That's the house next door."
"So they have lots of rooms that are alternate realities, like ours?"
"Yeah. You gettin' it?"
"I think so... So all the parallel Universe stuff where the Nazi's won is wrong?"
"Bcheeu!! That's mind blowing man!"