The link I added when I reenergised this thread, suggests there's a vague plausibility of going back in time, but not to murder your grandad thus yeeting ones self out of existence.I'd go back to the start of Apple/Microsoft/Amazon and buy in as much as possible
You'd have to go back to before the war and off Hitler with a sniper rifle at one of his earlier speeches and save millions and millions of lives.
Then back to 66 to see us win the world cup.
Was hoping one of our quantom specialists could shed light out on it.