The idea that you can’t go back in the past and kill your grandparents, since you would disappear is flawed. You can go back in the past and do anything and it wouldn’t have any effect on you since there is no place and no entity that is containing the past and that is controlling the “coherence” of the “story”. There is nothing containing the sequence of images, of pictures of Mass Energy configurations that lead up to the present, so you can go back to any past picture, to any past instantaneous picture and do anything with it.
You can say that the present picture is the result of all of the past pictures, that the present picture is the final number representing (and condensing) all of the past events and the present picture could only be exactly what it is only if all of the past intermediate pictures were exactly what they were. But it is a convenient way to look at it for our mind and decoding of reality, for our rules, thinking that the laws of physics constrained the pictures to follow only one path according to the trillions of quirk details that made up each preceeding picture. But the pictures are only a sequence of numbers, they are not related in any metaphysical way with each other, they are all disjoint and totally unrelated, they are only related in our mind and in our view.
Hence any past time travel is possible and will be achieved, just like any travel at all to any place or any configuration of Mass Energy at all, whether it be the past, the future, another wolrd or planet or anything at all, as long as the observer “remembers” the past as such, and experiences the interaction within the Box of Matter configured in a certain way as defined by our (arbitrary - mental and cultural) categories (past, future, other planet, whatever).
So time is not a story or something outside of itself, is not fixed and does not impose constraints on the coherence of the sequence of pictures, in essense it doesn’t exist, it is not some metaphysical item containing a story, it is invisible, only a process and only present in our mind as a variable.
It is always the same problem of what is a set of what, what is associated with what, what is a unit, what is a delimitation: the same problem with spatial items, how are their particles connected to each other ? and are they connected to each other ? are they in the same set, or is the set simply a delimited symbol in our formatting the world according to Intentionalities of Use and such.
So each picture (but a picture is a unit ? or is it also made up of a random group of disconnected particles assigned as one particle for our convenience ?) is disconnected from all the other pictures making up its past and future, so then the past and future of any picture can be any other picture, the path of transitions the pictures undergo while travelling from past to future can be any at all, any at all completely disregarding the constraints of the Laws of Physics that force the paths to go only in certain ways and directions. The real law of physics is simply the Transition, the change from one picture to the next, so any picture can be associated to any other, anything can be the past or future of anything else, going through any number of intermediate pictures at all, the more wild and random and unrelated the better: there is no metaphysical property that make the paths forced by the Laws of Physics any more real or important or true than any other, the only law is the law of change and the transition from one picture to the next, and the discovery of repetitive patterns (but always temporary, and imaginary and formatted by our Man Brain according to our rule and laws and arbitrary pain/pleasure circuits and such) on behalf of an Observer in the sea of pictures and the sea of paths, etc.
It implies that something is still connecting the present picture with the previous picture. That there is some particle, some monolithic dimensional slab connecting two pictures that form a relationship (but the relationship is just the sequence of numbers filling up some memory locations in our mind simulating repetitive patterns that become perceived as a unit, when they are just all random numbers, just numbers, memory locations meaning nothing and having no relationship with each other at all, since in reality, nothing has any relationship with nothing else, there are no relationships at all between anything, they are just associations, just sets made up of similar items that are conveniently manipulated by our quirky - fluke - arbitrary Man Brain and Mindform, etc.) But it is not so, each picture is independent and distinct and disjoint from the previous picture, there is no invisible thread linking them up as a story and as a necessity, hence time travel is possible in all directions, anything can be and anything can be assigned anyway at all.
Just because picture A came before picture B doesn’t mean that the transition from A to B is a necessity or a law of physics or an invariant. They just happened to occur one after the other but that design is irrelevant and could have been any other design at all.
I am questioning the very structure of “Cause and Effect” as something that is a necessity. All and any Cause and Effect can be decomposed into a set of particles colliding, they can be reduced into the collision and interaction of a set with another. But the entire set of interactions is just a painting, a picture, is just a design with no further reality or truth or necessity than the fact that they randomly just happened, and even if it weren’t random but designed, it just is, with nothing deeper or more important or any metaphysical property making that set of interactions any more important or deeper or real than anything else at all.
I find what you saying to be interesting, which is that there is no necessary connection between one event and another, which means there is nothing to tie them together. Now, this would be like have a whole bunch of dots on a sheet of paper, and there is no line to connect them one to another. Thus, they are all independent of one another.
But I do not see how this supports time travel into the past. First point is that there is no connection between you being alive in 2012 and going back in time to 1776. Remember, there is no connection amongst these things. The other point is that this assumes that the past exists. For in order to go back in time it seems that the past would have to exist. But if the past does not exist then you cannot go back in time.
What you can do is go to another event and think that you have gone back in time when you have not. You have just gone to another event, but this event might not be one of the past but just another one of the present.