π³π±
This would actually make a great story idea... basically the self-fulfilling prophecy time travel trope combined with the no matter what you do you cant change history time travel trope.
Hitler in the story would start out as a "good guy", kind, compassionate, loves people of all races, just wants to pain. But time and time again time travelers keep going back trying to kill him, always targeting him before he has body guards or power. Hitler doesn't know their time travelers of course. But every murder attempt inevitably fails (because it cant change history) and slowly changes Hitler into an evil person who hates humanity as an emotional response to each attempt on his life. So that the very act of time travelers trying to kill him is eventually what creates the monster Hitler turned out to be after all.
I fear though it might piss off way too many people, especially if it paints Hitler as a good guy in his youth as any representation of him as anything other than evil might be seen as being a pro-Hitler thing (even though I wouldn't see it that way since the novel would still portray him as evil int he end).
@trinsec Because he turned evil later in life and killed millions. The time travelers arent trying to kill him for who he was or what he did in his early life, only for who he was or what he did later in life. It just so happens the time travelers are the ones who caused the very thing they were trying to stop.
@freemo But if he turned evil later in life and killed millions, then the time travellers won't even matter. He will still turn evil later and kill millions, time travellers or no.
If the time travellers were the ones who caused the very thing, then he couldn't have turned evil later before the time travellers came into effect, so the time travellers wouldn't even had a reason to go kill him and...
Ye gods, am I seeing the end of the galaxy unfolding? Wow! It's a pretty sight!
;)
@trinsec There is no "before the time travelers came into effect". You are trying to evaluate cause and effect from a perspective that is outside of time in the first place, which doesnt work. The cause and effect here is circular: Hitler becomes evil because of time traveling hitman, time traveling hitman exist because hitler turns evil. There is no reality where hitler doesn't turn evil.
@freemo But isn't this called a paradox? What's the big bang for this one?
Kind of reminds me of 12 Monkeys. I should watch that movie again, that one was so confusing.
This is Mur 
@trinsec you might view it as a paradox, but it may be a perfectly valid representation of how time travel works all the same (then again it might not be, i mean time travel is very theoretical after all)
The more I understand quantum physics the more the idea of a casual loop makes a lot of sense to me. Consider two things.. first off in QM particles can just pop into existence out of nowhere. So at a very small scale causality doesn't hold true, it only holds true at larger scales. Two virtual particles (particles that dont quite exist yet but sorta do) will never turn into real particles unless they are consistent with reality in some way. In other words on a quantum level as long as there is self-consistency anything could happen (though may be unlikely).
So to me time travel with a causal loop makes perfect sense. There could be many different possible realities and the one that is true is the one that was always going to happen.
Let me explain it with a sort of example... lets forget about time travelers going back specifically to stop hitler from becoming evil for a moment and lets think about a reality kind of how your are thinking about it. That is before any time travelers are involved hitler is a nice dude, and just becomes a painter and no WWII. Now lets say some future time traveler who is just a psychopath for whatever reason really hates hitlers art and is just obsessed with killing the dude for no reason at all. Said time traveler tries to go back in time and tries to kill hitler. He fails but the attempt on hitler's life makes him bitter and ultimately turns hitler evil.. Now the future is changed, hitler from the perspective of the future isnt just a good guy painter but a legit bad guy, this time around the time travelers go back with the intent of killing hitler for being a bad guy, and they still wind up turning hitler evil for the same reason as before. But now the first reality is gone, time travel erased it. So all we really see is a relatity with a causal loop and we never see a "big bang" event because it never manifested, it was erased from all of space time by future iterations.
You can think of the first reality where hitler was a good guy a bit like a virtual particle, it never came into existance and became real because the real reality was always going to be the end result. It was basically a self-fulfilling prophesy that was always going to happen.
To put it another way you can think of time as something that changes and forms a totally new timeline maybe an infinite number of times every time a time traveler goes back in time.. this happens over and over again until finally it reaches a steady state where a casual loop happens, at that point that is the final time line and it is "stable" as it is self-consistent.
@freemo @trinsec If you look at it as a Minkowski 4-dimentional spacetime, causality is simply the rules for the relationship between Planck time units along the 4th dimension (assuming quantized time). We experience that spacetime as an incremental arrow-like progression along the 4th dimension. When information "travels" back to a lower point on the 4th dimension, as would happen when something at a later point in time (along the 4th dimension) also physically exists at an earlier point in time, then it's like making a non-linear or non-contiguous causal link to a lower point along the 4th dimension. An observer outside of the 4D spacetime doesn't experience "time" so you can't really say there are iterations as such because iterations require time and there is no such thing as time outside of spacetime itself. It just seems weird or paradoxical to us because we are stuck in this unidirectional arrow of experience along the 4th dimension.
@freemo I'm seeing a paradox there. If he was so good and compassionate to begin with, why would there even be any time travelers trying to kill him?