The idea you are referring to is known as the "grandfather paradox," which suggests that if time travel to the past were possible, it would lead to contradictions or paradoxes that challenge the existence of time travel itself. The paradox is often illustrated by the following scenario: If you were to travel back in time and prevent your own grandparents from meeting, it would create a contradiction because then you wouldn't exist to travel back in time in the first place.
The paradox highlights the potential logical and causal inconsistencies that can arise when considering backward time travel. It is one of the reasons why many scientists and philosophers believe that backward time travel, if possible, may be subject to certain constraints or safeguards to prevent paradoxes.
However, it's important to note that the paradox assumes a particular model of time travel and causality, which may not necessarily reflect the true nature of time or the rules that would govern time travel if it were to become possible. The paradox raises conceptual challenges but does not definitively prove or disprove the possibility of time travel.
It's worth mentioning that there are various theoretical proposals and interpretations that attempt to address the paradoxes associated with time travel, such as the Novikov self-consistency principle, which suggests that the laws of physics would conspire to prevent any changes to the timeline that lead to contradictions.
Ultimately, until time travel becomes a scientifically validated and established reality, the resolution of such paradoxes and the nature of time travel itself will remain speculative and subject to ongoing scientific and philosophical inquiry.