Ok, here we go,
If accordance to the pathways theory of time- every decision made breaks time into several different pathways (One for each possible outcome). Each one of those pathways then split at the next decision. It is my opinion that the universe once began with one path, and at each subtle change, the pathway split.
So if you were able to return back into time, you would have to secure the identity of each path. If you didn't do this, you would have literally trillions upon trillions (ect...) of dimensions to venture to. Each possibility within the history of the timeline pathway would...duh...be possible. So in turn, you could end up in any of the pathways in the history of time!
Therefore, if you were to identify the exact path, and you were to travel to it (laughable), and you were to kill your grandfather, that specific pathway would split once again- simply continuing on into a dimension in which your grandfather, father, you, your children, your children, their children, and so on, do not exist. The universe would not collapse, however it would continue into a mass of new pathways.
However in your timeline, you would no longer exist. So, your dimension would also split, and continue splitting normally forever.
Once again, in every concious change or decision or choice ever made in time, I feel that the time path has split. And each one of those sub-paths has continued forever, no matter if we're here or not. Thus, we exist in trillions of dimensions, just not exactly as we are now.
Just a thought, lol.
Thanks,
Alex
Edit-Typo