Much less than half the time. Remember, if Harry1 uses his time turner, he creates Universe2 with Harry2=Harry1_6_hours_ago. But in 6 hours, Harry2 will use his time turner, creating Universe3 with Harry3...
So IF there is a stable time loop of any kind, most universes will have that loop.
This raises the interesting prospect of stable sets of universes, with 6-hour histories A, B, and C. If a Harry that experiences A uses his time turner and does B, and a Harry experiencing B does C, and Harry experiencing C does A, then most copies of Harry will experience an inconsistent time loop, and it will seem like he actually went back and changed time.
If time loops are generally observed to be consistent, then this is evidence that single-state equilibria are much more probable than multiple-state equilibria.
Note that this explanation does not require Magic to simulate or calculate anything aside from creating a copy of a past state of the universe.
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: