He thought about that for a while. There wasn't exactly a good answer to that, but. "If it did. We'll never know. I mean. We can't. Either he's suddenly part of another timeline, and you'll go back and nothing will have changed for you. Or he'll go back to your universe and be exactly the same, and neither of you will remember, and nothing will have changed. Or you'll go back, and the your universe will still be there, but different. Or it have unraveled, in case I don't imagine you'll survive going back. The only way you'll ever know, is if you go back, remembering. In which case you'll know you've not destroyed everything. Am I right?"