Stepping Through The Mirror
Imagine a world in which every single action had an infinite number of possibilities and outcomes, every single choice we make is being played out somewhere in the multiverse. This infinite possibility would go right down to the sub atomic level, in which every particle would have an infinite number of positions into which it can occupy. Therefore an infinite number of universes would be existing simultaneously, right here, right now.
Using this as a hypothesis, would it be feasible to travel to any of the infinite worlds the hypothesis would allow, assuming that is, we had the technology available to us. This would create a set of interesting paradox's, one of which being travelling through time, and how it would effect the timeline of your universe.
Assuming this, the Grandfather paradox could be improbable. The grandfather paradox being a person travelling back in time to kill his grandfather before his father was conceived, would they be able to exist to do it. If a single timeline exists then this would be impossible, for if you prevent your father from being born, you could not exist and therefore not travel back in time to do the deed. With multiple possibilities being in effect, anything is possible, and is probably happening somewhere or some when. So would it be your grandfather you would be killing or one from a parallel universe, and if you managed it and still existed would you be able to return to your original timeline.
Along with travelling backwards and forwards in time and encountering strange paradox's, there could be a possibility to intentionally travel sideways and visit other parallel universes, some of which would be virtually indistinguishable from your own. Some could be so bizarre you could be of opposite gender, Hitler was victorious, the extinction of the dinosaurs did not occur and even the possibility that Elvis dodged the draft, gave up his music and became a time travelling operative of the secret service. How would you be able to predict where you would end up, would it be possible to select a parallel world to visit, if so what would you like to see.
So what we have now, put simply, for each possible universe there is a tree type structure emanating from every event, forming branches of possibility leading to other branches and so on. With parallel universes this tree structure would lead not just everywhere with layers of tree structures all stacked upon each other, but every when with every possibility thrown in for good measure.
A specific law of physics states that Matter cannot be created or destroyed in a chemical reaction. The universe being composed of matter, matter which is perfectly balanced to sustain itself. If someone was to travel to a parallel universe, how would it then effect the universe that the individual travelled to, and how much matter would be required to upset a universes balance, how would new matter interact with existing matter, would it be safe.
All this being said, if travel to the future, past or parallel universe is possible, would you sign on the dotted line and give it a go. I would, but where would I go.