Time Travel

[devonin]

But if you experienced two realities, then you are aware of both of them. You were there, you formed memories of both time periods and thus you will be aware of both tangents of existence.

You did not experience both realities. A nebulous future self that may or may not exist experienced one reality and went back in time to change it, resulting in the sole reality that you are aware of. From your present perspective, changing your own timeline to something other than what it is now is impossible, because you've already made all the changes you're going to. You just haven't gone back to do them yet.

You are already living the results of your future time travel endeavour and nothing about the world as it is seems to me anyway, like something has changed that should have been otherwise, and I suspect it is the same with everyone else.

Let's say you have a friend, Bob, who isn't a very popular guy. He would be murdered on the first of January, 2020, if someone doesn't intervene. But let's say that you go back in time and stop the assassin on the second of January, 2020. If that is history as it's meant to be, then history is also you going back in time to stop Bob's assassin. But how is this possible if history has shown no assassin? If you don't know about an assassin, why would you stop it? And if you don't stop it, won't Bob die?

In order for this to make any sense, we have to assume a situation where the present is say, 2021. Bob has been killed, and as much as nobody liked him, I decide "I'm going to go back in time to 2020 and stop that assassin!" This is where sci-fi likes to start talking about a paradox "If I stop the assassin, he won't die, but if he doesn't die, how would I know about the assassin to go back in time at all, so he'll die" and get a big and unnecessary headache about it.

The simple answer is, if in 2021, Bob has been killed, and it isn't until 2021 that you decide to go back in time to save him, then your 2021 self failed to stop the assassin. I can concieve of any number of reasons why you would fail. Perhaps you tried to stop him and he simply bested you before going on to kill Bob, perhaps you decided the potential risk to the timeline was too great and stopped, perhaps you were stopped by some sort of time police from further up your timeline, perhaps as in the case of a great Red Dwarf episode, you stop the assassin, and then realise that the results would have been worse than Dead Bob and carry out the killing yourself. Regardless, the fact that your 2020 necessarily included your 2021 self trying to stop the killer, and yet your 2020 also includes Bob dead, your 2021 self either failed or didn't try.

[Tokzic]

Originally Posted by devonin

In order for this to make any sense, we have to assume a situation where the present is say, 2021.

I actually said in my example that you decide to go back in time the next day, but okay, I'll roll with this if you'd prefer it that way.

Originally Posted by devonin

The simple answer is, if in 2021, Bob has been killed, and it isn't until 2021 that you decide to go back in time to save him, then your 2021 self failed to stop the assassin. I can concieve of any number of reasons why you would fail. Perhaps you tried to stop him and he simply bested you before going on to kill Bob, perhaps you decided the potential risk to the timeline was too great and stopped, perhaps you were stopped by some sort of time police from further up your timeline, perhaps as in the case of a great Red Dwarf episode, you stop the assassin, and then realise that the results would have been worse than Dead Bob and carry out the killing yourself. Regardless, the fact that your 2020 necessarily included your 2021 self trying to stop the killer, and yet your 2020 also includes Bob dead, your 2021 self either failed or didn't try.

This doesn't have anything to do with my post. My question isn't addressing what happens if Bob dies, but if Bob lives. If your 2021 self succeeds, Bob lives in 2020; but then you have no indication that you need to go back in time in 2021. Thus, you will not stop the assassin, and thus he dies. But he can't die, or else the timeline would change. So is it just impossible, or do you get the sudden premonition (well, "postmonition", but you know what I mean) that Bob will die unless you go back in time and save him?