I'm willing to bet most of them run on a non-negligible ammount of magic, though.
Descending through the illusory roof while invisible was a strange experience, and then Harry found himself in a metal corridor lighted with a dim orange light - which, Harry realized after a startled glance, was coming from an old-fashioned mantled gas lamp...
...for magic would fail, be drained away after a time, in the presence of Dementors.
But the others, maybe. Or maybe not; we also have
Minerva gazed up at the clock, the golden hands and silver numerals, the jerking motion. Muggles had invented that, and until they had, wizards had not bothered keeping time. Bells, timed by a sanded hourglass, had served Hogwarts for its classes when it was built.
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 81, which should be published later today. The previous thread passed 400 comments as of the time of this writing, so it will pass 500 comments soon after the next chapter is posted, if not before. I suggest refraining from commenting here until chapter 81 is posted; comment in the 12th thread until you read chapter 81. After chapter 81 is posted, I suggest all discussion of previous guesses be kept here, with links to comments in the previous thread.
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.) When posted, chapter 81 should appear here.
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: one, two, three, four, five, six, seven, eight,nine, ten, eleven, twelve.
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: