I think I would go back 25-30 years, find rahul’s mom, invite her out for a nice dinner. You know, then one thing leads to another, we go out on some more dates, share some good times and get to know each other well. She wanted to become a singer at one point, but it was a hard profession and she settled into a normal office job. Eventually, I meet her parents, we get along fine. Her dad is a respectable gold dealer, although he does not own any pure gold clothing. A couple of years into our relationship, we go on a nice vacation to Paris. I had brought along with me a modest but tasteful diamond ring and we get engaged on the Pont De Arts over the river Seine. We buy a nice house in the suburbs and live a peaceful life. I plant some flowers in the front, and we spend every Saturday morning having coffee at the neighborhood cafe. Soon we are blessed with a male child who we name “rahul”. We are overjoyed when our son graduates university and successfully gives the CFA L1 to pursue a job in finance. This is when I sit down with rahul and say to him, “my son, there is a great and powerful American internet website called AF. You must go there and spread my teachings that CFA will break you into FO from IT and that SRK’s abs are the best. Furthermore, the erection you experience is completely normal and natural. You must never waver from your mission to have every single member of this forum banned”. Such is how it has been written.
It doesn’t matter what we’ll do because no information about this trip backwards in time can ever be recorded without a net decrease in entropy. But my actions in the past must have consequences which suggest a present evidence of such thermodynamically irreversible event. This implies that such travel must be to a parallel universe/reality with its own arrow of time, where all present and future observers would have no knowledge of my trip back in time, I will have no memory of it, and the universe would have no record of it. Whether I have traveled back in time ever, or have always been here would be indistinguishable to anyone and anything. Metaphysically, you can assume that I (or anyone else) have traveled back in time to get here, because whether this truly happened or not is unobservable, undetectable and, in my view, essentially irrelevant without the notion of cause-and-effect, action-consequences associated with such hypothetical trip. So I’d argue that I, and anyone else who have traveled would be doing exactly what they are doing now since our present actions in any state of the universe cannot be contingent on such travel having occurred or not without allowing impermissible flow of information regarding such event.
On the scale of human perception measured by local observations (i.e., arguments that supposedly demonstrate you can’t go back like the grandfather paradox and its variants), it would seem that the necessity of closed causality chains is an unassailable assumption of the universe. This is true in the model of the universe as immutable slices of a frozen loaf, and appears to be the case even in the many-worlds hypothesis, where paradoxes can be “solved” as a temporal N-jump model where same-timeline interference is prevented by a branching off into a new timeline by the traveler, with the events of Timeline A undisturbed.
However, much in the way that universal constants and Newtonian determinism were superseded by findings of Special Relativity, General Relativity and Quantum Physics, I can’t help but think there is a twist somewhere to allowing a transformation in the perception of causality. Similar to how time dilation warped people’s minds when they realized that it was possible for two people to experience time at different rates from a stationary observer perspective.
Even the nature of time itself is not fully understood. It is one of those properties that almost require you to use it in the definition of itself. Describing it as a function of gravitational pull or relative velocity is informative, but it is not descriptive of the essence of the stuff itself. The same is true when describing time as a function of entropy as experienced by specks embedded in an inflationary universal substrate. Informative, but we do not fully understand the substance of time.
That said, it is easy to imagine that maybe causality doesn’t matter too much in the grand scheme, or maybe it only matters in areas of the universe where properties we observe hold true. Brian Greene talks about the idea that in an infinite universe, you have an infinite amount of particles that form and are driving infinite events and that somewhere, deep in space, there is a world where anything you can imagine is happening right this second. Further, there is no guarantee that the way the visible universe has unfolded with physical properties and constants settling where they did is necessarily true in a multiverse where initial embryonic conditions present in branching baby universes could be wildly different. What I’m saying is, somewhere there might be an explanation for how the principle of causality would be violated.
Having said all that, if I could go back in time my first act would be to become a mod on AF, so that I could argue against the banning of CvM, so that the AF community could be spared the living embodiment of unmitigated keyboard diarrhea that is quantwanttobe1996.