Harry Potter and the Methods of Rationality discussion thread, part 20, chapter 90

palladias

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.

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:

You do not need to rot13 anything about HP:MoR or the original Harry Potter series unless you are posting insider information from Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).

If there is evidence for X in MOR and/or canon then it’s fine to post about X without rot13, even if you also have heard privately from Eliezer that X is true. But you should not post that “Eliezer said X is true” unless you use rot13.

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:

You do not need to rot13 anything about HP:MoR or the original Harry Potter series unless you are posting insider information from Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).

If there is evidence for X in MOR and/or canon then it’s fine to post about X without rot13, even if you also have heard privately from Eliezer that X is true. But you should not post that “Eliezer said X is true” unless you use rot13.

I don't think so; he needs to use it himself at 6pm to transport everyone back, and smelly Harry mustn't go back himself. [EDITED to add: oops, I'm a twit; it looks like this works. So if this hack isn't viable in the MoRverse, it must be for some other reason, perhaps one of the ones below.]

My brain's fuzzy enough that I'm not confident there isn't some patch along those lines, though; if it turns out that there is, an alternative (which I can't rule out being already refuted by something in canon or HPMOR that I've forgotten) would be that a Time-Turner can transport at most one living person.

[EDITED to add: Actually there's an obviously better one, which is pretty clearly canonical and MoRonical (er, maybe that's not the best term): the 6-hour restriction is not per Time-Turner but per person. If that's "no more than 6 hours of time travel in any subjective 24 hours" rather than, or in addition to, "no further back than 6 hours", then as soon as Harry has a sixth-generation copy in his trunk, something bad happens, hence there is no consistent universe in which he gets a time-travelling army of size bigger than that.]

Of course another possibility is that (in the MoRverse and/or the Rowlingverse) this sort of hack is very much possible, but it seems like the sort of thing that would have been exploited to hell and back by ingenious folks like Voldemort and Dumbledore, so you probably get a more coherent fictional universe if there's some simple principle that prevents it.

The loop works because the conductor Harry that uses the Time-Turner at 6 PM is a younger version of the conductor Harry at 5 PM. Conductor Harry at 5:30 PM is going to go sit in the trunk at 6 PM, so he has no further need of the Time-Turner.

I think the most elegant formulation of a restriction that would prevent this (as well as all the things explicitly prevented in HPMoR) is that no path along which information or matter travels can stretch more than 30 hours per 24 hours.