According to our current understanding of physics, there is no scientific evidence or consensus on the possibility of going back in time and changing events in the past. Time travel, especially in a way that allows for altering the past, remains purely speculative and falls within the realm of science fiction.
One of the main challenges with the concept of changing the past is the potential for paradoxes, such as the aforementioned "grandfather paradox." If one were able to travel back in time and alter events in a way that prevents their own existence or changes the course of history, it leads to logical inconsistencies and contradictions.
The laws of physics, as we understand them, are based on cause and effect relationships. If one were to change an event in the past, it would disrupt the causal chain of events that led to the present. This raises questions about the conservation of energy, the consistency of physical laws, and the nature of reality itself.
It is worth mentioning that there are some speculative theories and thought experiments within the realm of physics, such as the concept of "closed timelike curves" (CTCs) and certain interpretations of quantum mechanics, that explore the possibility of time travel and altering the past. However, these ideas are highly theoretical and have not been experimentally confirmed.
In summary, while time travel and changing the past are fascinating concepts that have captured the imagination of many, there is currently no scientific consensus on their feasibility or the mechanisms that would make them possible.