You don’t actually know that Bob didn’t see the enemy at the pass, you only know that for some reason, Bob didn’t come back and tell you. Perhaps the reason he didn’t is because you would have sent that information back in time, and so he couldn’t.
Another possibility is that information loses “coherence” the further back it travels. (or forward, depending on which side your standing on) Think of it as a signal to noise problem—six hours isn’t the limit, it’s the limit of what we can correct for with the magic of the time turners. Prophecy seems to defeat the limit, but only by being nearly incomprehensible.
Or maybe it is possible, but insanely dangerous. There are hints that Atlantis was destroyed by something involving the time stream.
Perhaps the reason he didn’t is because you would have sent that information back in time, and so he couldn’t.
But every time someone uses a time turner, they send that information into the past. If it didn’t block them then, why would it block them now?
Another possibility is that information loses “coherence” the further back it travels.
There are ways of fixing that. For example, you could send people back in groups of three. Then you have them go back unless they’re stopped by at least two people.
Or maybe it is possible, but insanely dangerous.
That’s possible. The longer the time stream, the more likely that the closed time loop you end up with involves a hurricane or worse. I believe there was a book where the world ended because someone didn’t think about that. You could prevent it by allowing a “maybe”, so long as you make it likely enough that something you didn’t think of doesn’t become more likely.
Perhaps the reason he didn’t is because you would have sent that information back in time, and so he couldn’t.
But every time someone uses a time turner, they send that information into the past. If it didn’t block them then, why would it block them now?
Because you would have sent that information back in time. It didn’t block them “then” because they weren’t going to send the information further back. The effect could be more subtle—instead of preventing you from succeeding, it could prevent you from trying (don’t mess with time) or even make you not think of trying.
Another possibility is that information loses “coherence” the further back it travels.
There are ways of fixing that.
No, you can’t “fix” it, you can only reduce the effect. If a signal is weak, you can amplify it. But that only works up to a point. And apparently, that point is six hours, even with magical amplification and correction.
I believe there was a book where the world ended because …
I remember a short story by Larry Niven—Rotating cylinders and the possibility of global causality violation. The short story first appeared in Analog, was reprinted in CONVERGENT SERIES, and it contains the immortal line “I imagine the sun has gone nova”. Because the universe protects its cause-and-effect basis with humorless ferocity.
It didn’t block them “then” because they weren’t going to send the information further back.
They weren’t planning on it, but the information was sent nonetheless. P(Someone is going to go back and stop them from going back|They came back) < P(Someone is going to go back and stop them from going back|They did not came back)
But that only works up to a point.
Not really. The amount of time you can send back increases exponentially with the number of people sent back. If you only get it right a third of the time, sending one guy back only works a third of the time, but sending a hundred people back, you’d get about 67 +- 5 people sending the right bit, and you’d get it right about 99.98% of the time. If you have two hundred people, you’d get it right about 0.9999997% of the time.
They weren’t planning on it, but the information was sent nonetheless. P(Someone is going to go back and stop them from going back|They came back) < P(Someone is going to go back and stop them from going back|They did not came back)
That presupposes that P(Bob came back) is not affected by your decision to send the information further on.
I’m postulating that IF you would have sent the information further back, THEN P(Bob came back) = 0. Of course, it might not actually work that way, but if my supposition is correct, then Bob not coming back tells you nothing. The event only carries information if you aren’t going to make use of that information.
That presupposes that P(Bob came back) is not affected by your decision to send the information further on.
No. I gave an example in which it was not decided to send information back. It’s simply impossible to go back in time without proving that you weren’t killed by a time-travelling assassin.
You don’t actually know that Bob didn’t see the enemy at the pass, you only know that for some reason, Bob didn’t come back and tell you. Perhaps the reason he didn’t is because you would have sent that information back in time, and so he couldn’t.
Another possibility is that information loses “coherence” the further back it travels. (or forward, depending on which side your standing on) Think of it as a signal to noise problem—six hours isn’t the limit, it’s the limit of what we can correct for with the magic of the time turners. Prophecy seems to defeat the limit, but only by being nearly incomprehensible.
Or maybe it is possible, but insanely dangerous. There are hints that Atlantis was destroyed by something involving the time stream.
But every time someone uses a time turner, they send that information into the past. If it didn’t block them then, why would it block them now?
There are ways of fixing that. For example, you could send people back in groups of three. Then you have them go back unless they’re stopped by at least two people.
That’s possible. The longer the time stream, the more likely that the closed time loop you end up with involves a hurricane or worse. I believe there was a book where the world ended because someone didn’t think about that. You could prevent it by allowing a “maybe”, so long as you make it likely enough that something you didn’t think of doesn’t become more likely.
Because you would have sent that information back in time. It didn’t block them “then” because they weren’t going to send the information further back. The effect could be more subtle—instead of preventing you from succeeding, it could prevent you from trying (don’t mess with time) or even make you not think of trying.
No, you can’t “fix” it, you can only reduce the effect. If a signal is weak, you can amplify it. But that only works up to a point. And apparently, that point is six hours, even with magical amplification and correction.
I remember a short story by Larry Niven—Rotating cylinders and the possibility of global causality violation. The short story first appeared in Analog, was reprinted in CONVERGENT SERIES, and it contains the immortal line “I imagine the sun has gone nova”. Because the universe protects its cause-and-effect basis with humorless ferocity.
They weren’t planning on it, but the information was sent nonetheless. P(Someone is going to go back and stop them from going back|They came back) < P(Someone is going to go back and stop them from going back|They did not came back)
Not really. The amount of time you can send back increases exponentially with the number of people sent back. If you only get it right a third of the time, sending one guy back only works a third of the time, but sending a hundred people back, you’d get about 67 +- 5 people sending the right bit, and you’d get it right about 99.98% of the time. If you have two hundred people, you’d get it right about 0.9999997% of the time.
That presupposes that P(Bob came back) is not affected by your decision to send the information further on. I’m postulating that IF you would have sent the information further back, THEN P(Bob came back) = 0. Of course, it might not actually work that way, but if my supposition is correct, then Bob not coming back tells you nothing. The event only carries information if you aren’t going to make use of that information.
No. I gave an example in which it was not decided to send information back. It’s simply impossible to go back in time without proving that you weren’t killed by a time-travelling assassin.