I think the important bit here is that even if you could just “play time backwards” and watch again, there’s no reason to think you’d end up in the same Everett branch the next time around.
Makes perfect sense to me if you assume a single time-line. (This might be a big assumption, but probably less big than the truth of sufficiently strange prophecies.) You can think of this time line as having stabilized after a very long sequence of attempts at backward time travel under slightly different conditions. Any attempt at backward time travel that changes its initial conditions means a different or no attempt at time travel happens instead. Eventually you end with a time-line where all attempts at backward time travel exactly reproduce their initial conditions.
We know that we live in that stabilized time-line because we exist (though the details of this timeline depend on how people who don’t exist, but would have thought they exist for the same reasons we think we exist, would have acted, had they existed).
By the way, that sort of time-travel gives rise to Newcomb-like problems:
Suppose you have access to a time-machine and want to cheat on a really important exam (or make a fortune on the stock marked or save the world or whatever. The cheating example is the simplest). You decide to send yourself at a particular time a list with the questions after taking the exam. If you don’t find the list at the time you decided you know that somehow your attempt at sending the list failed (you changed your mind, the machine exploded in a spectacular fashion, you were caught attempting to send the list …).
But if you now change your mind and don’t try to send the list there never was any possibility of receiving the list in the first place! The only way to get the list if for you to try to send the list even if you already know you will fail, so that’s what you have to do if you really want to cheat. And if you really would do that, and only then, you will probably get the list at the specified time and never have to do it without knowing you succeed, but only if your pre-commitment is strong enough to even do it in the face of failure.
And if you would send yourself back useful information at other times even without having either received the information yourself or pre-commited to sending that particular information you will probably receive that sort of information.
Why was this post voted back down to 0 after having been at 2?
Newcomb-like problems are on-topic for this site and I would think having examples of such problems in a scenario not specifically constructed for them is a good thing? If it was because time travel is off topic wouldn’t the more prudent thing have been voting down the parent? The same if the time travel mechanics are considered incoherent (though I’d be really interested in learning why?) . If you think this post doesn’t actually describe anything Newcomb-like I would like to know why. Maybe I misunderstood the point of earlier examples here, or maybe I didn’t explain things sufficiently? Or is it just that the post was written badly? I’m not really happy with it, but I don’t see how I could have made it much clearer.
It’s an interesting point. It actually came up in the most recent Artemis Fowl novel, when he managed to ‘precommit’ himself out of a locked trunk in a car. :)
Depends if it’s type one time travel. Fictional examples: Twelve Monkeys, The Hundred Light-Year Diary.
I think the important bit here is that even if you could just “play time backwards” and watch again, there’s no reason to think you’d end up in the same Everett branch the next time around.
Insofar as I understand that page, that would mean that the world worked even less the way we thought it did.
Makes perfect sense to me if you assume a single time-line. (This might be a big assumption, but probably less big than the truth of sufficiently strange prophecies.) You can think of this time line as having stabilized after a very long sequence of attempts at backward time travel under slightly different conditions. Any attempt at backward time travel that changes its initial conditions means a different or no attempt at time travel happens instead. Eventually you end with a time-line where all attempts at backward time travel exactly reproduce their initial conditions. We know that we live in that stabilized time-line because we exist (though the details of this timeline depend on how people who don’t exist, but would have thought they exist for the same reasons we think we exist, would have acted, had they existed).
By the way, that sort of time-travel gives rise to Newcomb-like problems:
Suppose you have access to a time-machine and want to cheat on a really important exam (or make a fortune on the stock marked or save the world or whatever. The cheating example is the simplest). You decide to send yourself at a particular time a list with the questions after taking the exam. If you don’t find the list at the time you decided you know that somehow your attempt at sending the list failed (you changed your mind, the machine exploded in a spectacular fashion, you were caught attempting to send the list …). But if you now change your mind and don’t try to send the list there never was any possibility of receiving the list in the first place! The only way to get the list if for you to try to send the list even if you already know you will fail, so that’s what you have to do if you really want to cheat. And if you really would do that, and only then, you will probably get the list at the specified time and never have to do it without knowing you succeed, but only if your pre-commitment is strong enough to even do it in the face of failure.
And if you would send yourself back useful information at other times even without having either received the information yourself or pre-commited to sending that particular information you will probably receive that sort of information.
Why was this post voted back down to 0 after having been at 2? Newcomb-like problems are on-topic for this site and I would think having examples of such problems in a scenario not specifically constructed for them is a good thing? If it was because time travel is off topic wouldn’t the more prudent thing have been voting down the parent? The same if the time travel mechanics are considered incoherent (though I’d be really interested in learning why?) . If you think this post doesn’t actually describe anything Newcomb-like I would like to know why. Maybe I misunderstood the point of earlier examples here, or maybe I didn’t explain things sufficiently? Or is it just that the post was written badly? I’m not really happy with it, but I don’t see how I could have made it much clearer.
It’s an interesting point. It actually came up in the most recent Artemis Fowl novel, when he managed to ‘precommit’ himself out of a locked trunk in a car. :)