My theory is that like it is said, for every possibility of every moment a new alternate reality is created. The effect is like a tree, and like a tree time cannot go backwards but what if you were to jump onto a shorter or longer branch which is more or less advanced? Of course there would be little if any control as to where you are going and thus you probably could not go back to the original branch intentionally. Since all the matter would be overlapped in a common (summary) universe, the universe would not overflow. Maybe these universes are simply different frequencies of energy, the frequencies generated by photons or something else of the sort. Of course the biggest danger of this would be jumping into a reality where the atmosphere of the earth is different or where the earth does not exist. Maybe there is a relation/common factor between all space?