The question of time travel and its implications on causality and the nature of reality is still a subject of debate and speculation among scientists and philosophers. The concept of time travel introduces complex paradoxes, such as the grandfather paradox, which raises questions about the possibility and consistency of traveling back in time.
In some theoretical models, time travel is thought to be possible within the framework of certain physical theories, such as general relativity. However, even if time travel were to become a reality in the future, it doesn't necessarily mean it already exists in the present.
One possible explanation is that time travel could be constrained by certain limitations or yet-to-be-discovered scientific principles. It's also possible that if time travel is ever achieved, it could only be achieved from the point in time when it was first invented or discovered, creating a sort of "temporal barrier" preventing travel to times prior to its invention.
Ultimately, the nature of time travel, if it is possible at all, is still uncertain. Speculating on its implications and whether it exists in the present is purely speculative and falls into the realm of science fiction.