Don't know what it's called but, me favorite paradox was on doctor who. Short and curly of it is, a guy really likes Beethoven's music so he travels back in time to have Beethoven sign his sheet music only to find out Beethoven doesn't exist. He becomes Beethoven.
Idk what this paradox is called exactly. (I would appreciate if someone could give me the name) So somebody goes back in time to, lets say kill hitler, and they go back and succeed in their mission and hitler is dead, but now that hitler is dead the timeline in the future would have had no hitler, therefore making it so that the person who killed hitler would have no reason to go back in time and if they never went back in time they never killed hitler. And thus a paradox is born
I come across my older self. He gives me a timemachine.
"Were does the timemachine come from", I ask.
"You gave it to me", he responds. Where does the timemachine come from?
People really need to look up the definition of a paradox before answering.