The title is the best way I could group this thought. And the following is most likely sloppy so I do apologize. I get the 'feeling' (subjective I know), that the measurement effecting the outcome i.e. only being able to measure position over velocity, collapsing wave functions, etc... comes down to proof of choice. If the interactions of our choices are free to occur without any pre-destination then the concept of time travel is meaningless. I.e. in order for time to travel to work at any point it would mean a specific order of events would have to occur and thus the 'paradox' but also the forced realization that there is no choice. If there is a choice free from any future fixed point then time travel is simply not possible. In thinking of that it occurred to me that this holds greater implications than just 'time travel' but also effects the interactions and measurements of physics. for if I imagine the 'ordered' system of the universe without chaos by removing the human element then it seem to run in a predictable manner and 'future' events could always be predicted perfectly. Add the human element in to the system and predictability either becomes impossible with time travel impossible and any measurement of wave function or particle completely dependent upon that measurement and not translatable 'perfectly' to another or it becomes exponentially larger to calculate and time travel is possible and the results of all measurements are predetermined to keep the time line. So it's not really a paradox but a choice, you have one or the other not both as they are two separate operating systems. Physics and science in general seems to try and separate out and ignore the human element. We have a direct effect on the system but how does one measure that accurately? every measurement only supports what was trying to be measured when your part of the system being measured.