The Novikov self-consistency principle is a concept in theoretical physics that addresses time travel and its paradoxes. It suggests that any actions taken by a time traveler in the past must be consistent with the timeline that already exists. This means that events cannot be changed in a way that creates contradictions or alternate realities. According to this principle, if a time traveler were to go back in time, their actions would ultimately lead to the same outcome that has already occurred. This ensures that the timeline remains coherent and avoids paradoxes, such as the famous grandfather paradox, where a time traveler could potentially prevent their own existence.