Chapter 61: 'There was another pause, and then Madam Bones's voice said, "I have information which I learned four hours into the future, Albus. Do you still want it?"'
This seems like a useless question. A bit of information was already conveyed representing the fact that Amelia Bones was 4 hours into the future & found some information that would be useful to Dumbledore. Is this not sufficient information transfer in and of itself to prevent Dumbledore traveling backwards?
Sorry if I'm confused, but reasoning about time is hard, and my diagrams are not as helpful as Snape's and Dumbledore's.
I think the info was sent to Bones rather than her finding it and going back, but your point may still stand. Perhaps "somebody sent something back to Amelia Bones" is vague enough to slip past the filter. There must be some nonzero cutoff, because otherwise the info would affect the whole future (from the point of receiving the info) light come of anyone who got time-traveled info, and the whole earth would be interdicted whenever somebody went back.
If I'm wrong about that, it's possible that either Bones or Dumbledore wasn't thinking, or Dumbledore realized that he was already blocked and that's part of why he decided he wanted the info.
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.