Umm.. since i was 10? around there.. thats when I was really interested in time and dimension traveling.. I would stay up for hours on end just looking at my ceiling wondering it is possible...
Thats when I came up with the Grandfather theory, but a few months later my friend told me that somebody else already thought of that theory, which made me pretty much give up on philosophy... besides, I already figured it out on my own.
The only way for time travel to be trully possible is if there are alternate dimensions. Everytime we break the space-time barrier, we create a whole new universe. Which would stop this universe from collapsing because of the who time paradox thing, because we'd be trapped in an everlasting circle if time travel is possible, unless of course, for the dimensions.
When we go back in time, we wouldn't go back in a time and change something, it would effect us being born, unless its a different dimension, then we'd effect ourselves of being born, but limited to that dimension. So we will still exist in that dimension, because we are from a different dimension. Thus enabling us to roam that dimension in the past. My theory is we still wouldn't be able to return to the future as we want, because we wouldn't be able to control which dimension we would be going to, or if a dimension would form in the first place. If anything, time travel will cause the universe itself to collapse. So in a way, time travel is the end of the world. Its a good thing its not possible,
If dimension exist, then time traveling exists. But it would do no good, because you wouldn't be changing your direct past anyway, just a different dimensional version of you's past.