The concept of time travel, particularly backward time travel, is largely a subject of speculation and hypothetical scenarios, as it is not currently known to be possible according to our understanding of physics. Therefore, questions about how the universe "knows" or enforces certain actions to maintain a consistent timeline are purely speculative.
In various works of fiction and some theoretical discussions, the idea of a "self-correcting" or "self-consistent" universe is sometimes proposed. According to this notion, if time travel were possible, any actions taken by a time traveler would ultimately lead to events that ensure the preservation of the timeline and prevent paradoxes.
For example, if someone were to travel back in time and attempt to change a significant historical event, the universe might present obstacles, coincidences, or other circumstances that prevent the alteration from occurring. Alternatively, the time traveler's actions might inadvertently contribute to the very event they intended to change, thus preserving the original timeline.
However, it's crucial to remember that these are fictional or speculative ideas and do not reflect our current scientific understanding. In reality, the nature of time, causality, and the consequences of time travel, if possible, remain largely unknown and subjects of ongoing scientific investigation and theoretical debate.
It's important to approach discussions about time travel with a healthy skepticism and recognize that our understanding of the topic is limited, based on current scientific knowledge.