I take the following view of the past: Â Anything that happens stays happened. Â Once an event has passed, it cannot be altered, even if time travel is something that eventually comes to be. Â If one was to try and go back in time and (for example) assassinate Hitler, one would be unable to because it is an even that has already taken place. Â I like multiple universes as a fictional idea (particularly Heinlein’s fictons idea, where any book you read is actually telling a story about real people in some other dimension) but I think the real world is more solid than that. Â This leads me to the following conclusion:
Since I have no recollection of somebody who looks like an older me coming back and punching me in the head and telling me not to make <mistake x>, I’m pretty sure time travel is not invented/discovered in my lifetime.  I expounded on this idea to Amy earlier in the week and she suggested that maybe I just haven’t made a mistake big enough yet.  I guess it is also possible that, since this face-punching never took place, even if time travel were invented, the face-punching could/would not have taken place.  You start to run out of verb tenses in a hurry when discussing non-linear time events.  I do know this.  In the event that I meet somebody with my name who looks just like an older me, I will pre-emptively  punch him and then steal his time machine.  Teenage Adam has some straightening out to do. Â