Harry Potter and the Methods of Rationality discussion thread, March 2015, chapter 119

Gondolinian

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 119.

Plans for next chapter release:

Ch. 120 will post on March 12th, 2015 at 12PM Pacific Time (7PM UTC).

The next long chapter will be Ch. 122, posting on March 14th, 2015 at 9AM Pacific / 4PM UTC.

There is 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.)

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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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.

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 119.

Plans for next chapter release:

Ch. 120 will post on March 12th, 2015 at 12PM Pacific Time (7PM UTC).

The next long chapter will be Ch. 122, posting on March 14th, 2015 at 9AM Pacific / 4PM UTC.

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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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 figured that the two were equivalent. If we find something that magic does not consider information (but we do), we can use it to receive information from an arbitrarily far future.

For example, suppose that magic does not consider merely "Does a timeturned person show up at time T at this location or not" to be information, and we want to know if the world ends in the next 10 years.

Four people with time-turners agree to the following scheme (using Unbreakable Vows if necessary):

If, at 12:01 AM on March 14th, 2025, the world has not ended, Alice goes back 6 hours using a Time-Turner.
If, at 6:01 PM on March 13th, 2025, Bob sees Alice appear out of nowhere, he goes back 6 hours using a Time-Turner.
If, at 12:01 PM on March 13th, 2025, Carol sees Bob appear out of nowhere, he goes back 6 hours using a Time-Turner.
If, at 6:01 AM on March 13th, 2025, Dan sees Carol appear out of nowhere, he goes back 6 hours using a Time-Turner.
If, at 12:01 AM on March 13th, 2025, Alice sees Dan appear out of nowhere, he goes back 6 hours using a Time-Turner.
...

Also, they make sure that in case of anything not world-ending, they will have a substitute available so that the chain will not break.

After agreeing to this, if Alice sees Dan appear out of nowhere at 12:01 AM tomorrow, then they know that the world has not ended. If not, then something sufficiently bad to cause the chain to break must have happened in the next 10 years. (Either way, they must continue to implement the plan for as long as possible.)

Using further chains of Time-Turners, we can use our favorite unbounded binary search scheme to narrow down a more precise date for the world ending.

(Edit: actually, we can probably improve the resolution simply by using the Time-Turners at a different specified time depending on circumstances.)

I think this is taking "6 hour limit" way too literally, when by far the simplest explanation is that time turners can protect you against Time's tendency towards simplicity for 6 hours or so, but if you try to chain that, it becomes overwhelmingly computationally simpler (and therefore more likely) for the intention to set up such a chain to result in the death of everyone involved, than for the chain to work as designed.