Nowadays physics are based on the fact that matter matters, it's all about energy and matter, that are the same thing as we all know.
But there's something that kepts been ignored by physics, and it's so much ignored that quantum physics say that time it's not part of equations allowing them to time travel at quantum level.
The fact is that time is the primordial thing in universe, there are so called two "spaces" that we can move on universe, the matter line, our tridimensional or more space, and timeline, but you can't move on matter space without movindo through the timeline, but indeed you can move at timeline without moving on space.
So it means that time isn't the result of the creation of space, meaning that space is the result of time, so time existed before this universe could ever exist.
The reason we can't travel back in time is because it is a power that's beyond limits of or limited universe, matter on the other hand, can be easily manipulated to be whatever we want...