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 w...
The next discussion thread is here.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 85. The previous thread has long passed 500 comments. Comment in the 15th thread until you read chapter 85.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15.
As a reminder, it’s often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: