Statua santo onofrio

A predestination paradox, also called a causal loop or causality loop, is a paradox of time travel that is often used as a convention in science fiction. It exists when a time traveller is caught in a loop of events that "predestines" him to travel back in time. This paradox is in some ways the opposite of the grandfather paradox, the famous example of the traveller killing his own grandfather before his parent is born, thereby precluding his own travel to the past by cancelling his own existence.

Because of the possibility of influencing the past while time travelling, one way of explaining why history does not change is by saying that whatever has happened was meant to happen. A time traveller attempting to alter the past in this model, intentionally or not, would only be fulfilling his role in creating history, not changing it.

In physics, the Novikov self-consistency principle proposes that contradictory causal loops cannot form, but that consistent ones can. il XV secolo Sant'Onofrio anacoreta è patrono principale dell dei tre territori, il Santo anacoreta fosse patrono solo di centro trovava posto la statua dell'Immacolata e ai lati. In a physical sense, a self-consistent causal loop of this kind is not actually a paradox because it produces a logically consistent result rather than a contradictory one. It is only perceived as a paradox because it goes against conventional expectations and assumptions about causality.

Examples

A typical example of a predestination paradox is as follows:

A man travels back in time to discover the cause of a famous fire. While in the building where the fire started, he accidentally knocks over a kerosene lantern and causes a fire, the same fire that would inspire him, years later, to travel back in time.

Another example:

A man travels back in time and impregnates his great-great-grandmother.