Harry's universe may not be Turing computable in the absolute sense assuming that arbitrary time travel is possible, but with even minor limits you can come up with algorithms that largely work, or will work most of the time.
As an example, run the simulation forward taking snapshots at every point until a backward looking event occurs. Take the snapshots of the two time periods and brute force search for a solution (any solution) that can link the two time periods together without breaking constraints. If a solution is found, throw all the intermediate snapshots away and replace them with the found solution. Otherwise, keep the existing data and fail the time travel event in some fashion.
My understanding is that it is possible to find solutions to these kinds of problems (otherwise we wouldn't know and busy beaver numbers.) It's just not possible to find them via some general, easily computable algorithm.
This could explain the six-hour limit on Time-Turners - that's the maximum lookback the Atlantis algorithm allows.
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 90. The previous thread has passed 750 comments.
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, 16, 17,18,19.
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