Really thank you, Alejandro1, you clarified the "inertial reference" point.
Going a little bit beyond, what the heck the gravity has to do with time turners and time travel? My knowledge is pretty restrict in this area (almost zero), so if you can't answer this in a simple way [1]; just saying "go study X" will work fine,too, if that's the case.
[1] As Feynman says, if you want to explain something complicated for someone, you can rephrase or use analogies as long as the person has an (or a few) equivalent model of that topic in their reality. So, if the topic requires some model that I don't own by not knowing lots of relativity, just point that out so that I can study and not lose good threads like this in the future. Thanks.
So, in this fic, you time travel and you wind up in the "same place" as you started. The concept of "same place", however, is actually really complicated. The earth is spinning and orbiting the sun, which is itself orbiting the center of the galaxy, which is in turn....
My first intuition was that, if you traveled in time, you would wind up floating in space. However, it's not at all obvious that a reference frame where the sun is stationary is better than any other, which is how I got to using your current stationary inertial reference frame: it's the only one that's unique from all the other possible ones, and yields the behavior above.
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: