Time Travel and Parallel World

There is an interesting discussion going on in Facebook National Geographic page and what interest me is that people are so eager to explore such possibilities.

I feel that in order to understand time travel, we need also to understand parallel world. The fact that in this dimension of time-space we are relying too much on logic and specialize skills. Therefore, a lot of time, a lot of information are lost. Such are the case, that progress can't be made.

Let me quote a classic example what I mean. If Leonardo Da Vinci had invented his flying machine

five hundred years ago, then Henry Ford and the Wright Brothers would have been in the parallel universe. Their invention will prove useless since we would have Da Vinci's invention in this dimension of time space.

Having said that, time travel would not have been possible as the invention was not being created. However, in the parallel world, where Da Vinci's invention was made, all hell broke lose. Flying saucers, time travel, etc.

If we had just concentrate on time machine alone, not understanding the concept of parallel world, nothing is going to work.

I'm more concern about traveling between dimensions as in the TV sitcom Sliders. If that really happens, that is the real "ALL HELL BROKE LOSE".