- Closed Loop
My presence is defined by the continuous nature of my existence from past to present in my own reference frame. Therefore, if I change the past I change the future and I change myself. This changes what I do to the past which again changes me and my actions and so on with infinite recursion sorted out in zero time until the past creates a future which creates that specific past and that is always what is visible by a historian standing after the time loop. In this model you always provoke your own time travel because if that wasn't the case you'd just go through a spiralling montage of infinite different versions of the events until that was true. - Non Causal
My presence is defined by the present in the current reference frame. Therefore, if I change the past I am simply there changing the past. The future will be different, but I am still there as an actual independent object experiencing the past as my present day. In this model, once the past has been changed the future that a time traveler remembered will necessarily no longer exist. Indeed, every traveller in time comes from a future which will never happen so that any outside observer will see them as appearing in the time stream having not been caused by anything at all.
Non Causal seems more likely to me based on the observable evidence of what happens when, for example, one is confronted by a person who has experienced more time than you (as happens every time you move faster than those you meet). And while the Non Causal time travel has an elegant and plausible answer to the grandfather paradox and the free lunch paradox, there is another thing that has been plaguing me: the occassion of two time travelers.
Imagine for a second that a time travel named Abe goes back to 1970 in Detroit to bet on the horses. During this limited window there has yet to be enough crushed butterflies for the results to be appreciably different, so he can make a lot of money. But that's not important. The important thing is that in spending his period gambling and whoring in ancient times with his sports almanac, Abe has created a new future that will come into being after fifty years - that is Abe will go through his entire life, grow old and die and there will be a single future capable of creating time travel some time down the line.
So, out of this one new shining future (where interestingly enough, Abe is never born), there comes a new time traveler named Josh. He goes back in time and changes stuff - what happens to Abe's experience? I assume for the moment that he appears in 1970 with his sports almanac from a future that no longer exists and he is confronted with a 1970 that he does not recall.
What if Josh kills Abe in 1970 and then goes back even farther and creates a history where Detroit is never built and Abe doesn't stay there - is Abe still alive? Where in the time stream would he appear?
-Username17