I saw a question on “zhihu”, someone ask a question about time machine, why there’s no one come back from the future, but always people in the contemporary fly to the future world. So interesting a question, kinds of answer give me a good lesson, and i first know a theory named grandfather paradox.
is meant the time traveller went back to the time when his grandfather had not married yet. The time traverller kills his grandfather at that time, and therefore, the time traveller is never born when he was meant to be. If he is never born, then he is unable to travel through time and kill his grandfather, which means he would be born, and so on.