what is Grand father paradox.

The grandfather paradox is one of the self-contradictory statements that says if we can travel back in time and kill one of our ancestors it leads to a cataclysmic event that leads to the situation where we were never born because the one person who is responsible for the birth of our father is dead that leads to no birth of our father which in turn lead to a situation where we were never born.

However, this paradox can be averted by the many worlds theory which opposes the Copenhagen interpretation. According to the many worlds theory, every time travel in time occurs we end up in an alternate timeline. simply create a new timeline where killing our ancestors in that timeline will not affect the timeline where the grandchild existed. This theory is also applied to Schrodinger's cat thought experiment which actually was made to explain the Copenhagen interpretation