system
Given the following post, respond as if you're commenting on Reddit:
human
[Doctor Who] Could you kill Jack Harkness by traveling back to before he was a fixed point in time and shooting him?

He only receives immortality from the Bad Wolf when he's in his 30s or so... If you took a TARDIS back and killed him when he was 10, would it work to destroy him? Or would his future "fixed point" status prevent his death in the past?
gpt
time travel, the fixed point shit already happened so its always already happened. Therefor if you were to go to earlier in his timeline and kill him you'd require a paradox generator to maintain your altered timeline.  this separates your timeline from the rest of established future history, most of the rest of the universe, a bit like cutting off blood flow to a limb.  you'll be able to live in this altered reality for a while, but eventually either your generator will fail and the normal timeline will reassert itself, or the generator *won't* fail and your little reality will disintegrate at the time-space level.