In this category I’ve been telling you a lot of ways to time travel, but in here, I’ll be telling you about a reason not to.
The grandfather paradox is a scenario where a time traveler does something that then prevents themselves from doing said thing. A good example, by physicist John Garrison is that a machine that sends a signal through a time machine to shut it off, and gets the signal before it sends it, which means that it cannot send it. There is also the ‘Hitler Paradox’ where somebody goes back in time to kill Adulf Hitler before he starts World War II and The Holocaust, but then that somebody would have no reason to travel back in time to kill Hitler who is already dead.