According to our current understanding of physics, there is no evidence or theoretical framework that suggests it is possible to alter the past in a way that would change events that have already occurred. The concept of altering the past is often associated with time travel and has been a topic of fascination in science fiction.
In classical physics and in our everyday experience, time is viewed as a linear progression from the past to the future, with events occurring in a fixed order. However, with the advent of Einstein's theory of relativity, our understanding of time has become more complex.
In the realm of general relativity, which describes the gravitational interactions and the geometry of spacetime, there are solutions that allow for the theoretical possibility of closed timelike curves (CTCs). These are paths in spacetime that, if traversed, would allow an object or information to return to an earlier point in its own history.
While the existence of CTCs is permitted within the framework of general relativity, they come with significant challenges and paradoxes, such as the famous grandfather paradox. The grandfather paradox raises the question of what would happen if one were to travel back in time and prevent their own birth, thereby creating a logical contradiction.
To date, there is no experimental evidence or practical demonstration of backward time travel or the alteration of the past. Furthermore, the existence and stability of CTCs remain speculative and highly hypothetical. Theoretical physicists continue to investigate the nature of time, the implications of time travel, and the consistency of such scenarios within the framework of quantum mechanics and general relativity.
It's important to note that the limitations and constraints imposed by causality, the conservation of energy and information, and the arrow of time make the idea of altering the past highly unlikely according to our current scientific understanding.