Celestia tried to think of a way to explain.  “Think of it like two rivers.  One river is ‘your’ universe, the other, is mine.”  He was a bit perplexed by the sudden analogy, but waited patiently for her to continue.  “If I were to pluck a pebble from the bed of your river, and toss it into my river, do you think that because I removed matter from one river and added it to another, realities will cease to exist?” 