  a predestination paradox (also called causal loop, causality loop, and, less frequently, closed loop or closed time loop) is a paradox of time travel that is often used as a convention in science fiction. a temporal causality loop is an event whereby a specific moment in time repeats itself continually inside an independent fragment of time. the paradox occurs when a time traveler is caught in a loop of events that "predestines" or "predates" him or her to travel back in time. the paradox suggests that those people who travel back in time would have no way of changing a situation. one good example of a predestination paradox is someone traveling back in time to save a loved one from a car accident, only to find themselves driving the car that killed the family member or friend. this type of occurrence gave birth to a new name for this paradox, which is often called a causal loop or a closed time loop. if, hypothetically speaking, people find themselves in this situation, then they are forced to repeat it over and over again, thus remaining literally trapped in a loop. this paradox completely opposes the grandfather paradox, which states that if someone goes back in time and kills his or her grandfather, then the entire event would be impossible, as he or she wouldn't have been born. the paradox does not necessarily imply a higher plan from some higher power. it merely affirms a belief that time is immutable. the series of events can still simply be from causality rather than from some form of higher plan, such as: event a. mad scientist meets delusional madman mumbling about time travel mechanics; event b. mad scientist devotes his life to proving time travel, ignoring his wife and kids who leave him; event c. mad scientist decides to travel back in time to prevent this; event d. time travel turns mad scientist into delusional madman. predestined in the sense that causality is immutable, not there was necessarily a plan involved. because of the possibility of influencing the past while time traveling, one way of explaining why history does not change is by saying that whatever has happened must happen. this means either that time travelers' attempts to alter the past in this model, intentionally or not, would only fulfill their role in creating history as we know it and not change it or that time-travelers' personal knowledge of history already includes their future travels in their own experience of the past (for the novikov self-consistency principle). in other words: time travelers are in the past, which requires that they were in the past before. therefore, their presence is vital to the future, and they do something that causes the future to occur in the same way that they remember. it is very closely related to the ontological paradox and usually
Causality Fiction Physical_paradoxes Plot_(narrative) Time_travel