The predestination paradox.

   

     The predestination paradox is a hypothetical situation that arises when time travel is involved and which seems to contradict the laws of cause and effect. It involves a person traveling back in time and causing events to unfold in a certain way, which would mean that their actions in the past were predetermined by their actions in the future. For example, suppose a person travels back in time and prevents a disaster from occurring. 

        This would mean that their actions in the past were responsible for the disaster not happening, but it would also mean that their actions in the future (i.e., traveling back in time) were caused by the disaster not happening. This creates a paradox because it suggests that the cause and the effect are happening simultaneously, which seems to violate the laws of cause and effect. It is important to note that the predestination paradox is purely theoretical and does not necessarily indicate the nature of time travel. Some physicists believe that the laws of physics may not allow for the possibility of time travel, while others believe that it may be possible under certain circumstances.