Which seems to be unknown to 7th year students of Hogwarts.

It was hard to muster a proper sense of indignation when you were confronting the same dignified witch who, twelve years and four months earlier, had given both of you two weeks' detention after catching you in the act of conceiving Tracey.

Sigh. Magical education is seriously lacking.

I wouldn't expect Wizards to be big fans of birth control or abortion.

Why not?

There are only thirty hours in a day and every child means greater demands on your time. It's not like they can hire muggles to raise their kids, like affluent muggle families might hire less-affluent folk to look after theirs. And we don't hear about anyone being raised by house elves.

Why wouldn't they want sex without conception?

the base could be a trained component like muscle strength

If it worked like that, there’s still the question of “what component?” Muscles becoming stronger as a result of exercising them is a complex behavior, governed by many genes. Harry’s reasoning towards one “magic marker gene” suggests that is not the case.

I can think of all sorts of possible explanations, I just can’t see one that looks really reasonable; since we have no actual explanation about how stuff works, you need a lot of assumptions for anything and stuff tends to be arbitrary. If you think about it, all substances being combinations of four elements, or Lamarckian inheritance, are plausible explanations if your only observations are on the level of “some stuff burns” and “water quenches fire” or “children kinda look like parents”.

(“Inventing” new charms is mentioned several times, but there are basically no details about how that works. Harry just changes how to apply a couple of existing charms, and he seems to have figured out how he might pick ingredients for potions, but even there he’s not told where the gestures and ritual come from.)

Oh, no, he did much worse:

He switched her brain with that of a chicken (with Magic!), then burned the chicken alive—in her body—so that the chicken’s thrashing around in horrible agony left marks around the room (while he forced Narcissa to watch, with Magic!). Then he kept Narcissa alive (with Magic!) in the chicken’s body, to keep company to Fawkes; he kept her hidden (with Magic!) right near his perch, so that every time Fawkes re-spawned she was reminded of what her captor was capable of. Then he burned her in front of Harry (with Magic!) just because he thought it was funny :-)

By the way, Lucius is not actually mad because he killed her—Dumbledore told the first part the above to him, but he kept silent about the details because it was embarrassing to have his wife turned to a chicken. That’s why Dumbledore had trouble during the trial; he felt a bit embarrassed about having killed Narcissa after all.

Also, Draco actually picked “fire” as his army’s symbol because he’s secretly fantasizing about being burned alive.

If you’re going for “what’s going on”, you might as well ask where does the “excessive” come from. I mean, you could switch to a “lever” instead of a “button” analogy to “justify” that the magician provides energy for the “magical mechanism” of a spell, but the ridiculous amounts of energy implied by even some low-level spells means that won’t actually explain much.

(For example, first years can fly broom-sticks with non-Newtonian mechanics. This either means that a large amount of energy is used to simulate them over normal physics—compensating for inertia with very high accelerations—or that the “normal” physics is actually simulated on a completely different real physics substrate, in which case all bets are off.)

Also, the reasoning for the single-magic-gene, if true in-universe, raises the question of where do all differences in magic ability come from. Sure, Harry considers training and conscientiousness and talent, but only that seems to me not enough to explain differences that we see. Alohomora is explicitly said to balance the casters’ magic powers, and the interaction of many spells (e.g., shields and shield-breakers) are seen to depend on the relative ability of the casters.

There are huge differences of ability between a talented painter and the average person, but that would only explain stuff like creating spells. Pushing a button on a printer works the same for both.

And in the “lever” analogy, just as relative strength is not governed by a single gene, differences between magical power are hard to explain with a single gene. (Even if there are more than two alleles, some of which are magic but with varying strength, and some of which are not, that should result in quantified levels of power rather than what appears to be a continuum.)

I would just go with a combination of “it just ignores the rules” and “intuitive user interface”. If whatever causes magic allows spells like Somnium, it can make you progressively tired and then unconscious as you exhaust your magic ration, just to make a point.

Here's a question: how does excessive magic use cause unconsciousness? What's going on there, physically?

Ok, this is quite old stuff, and maybe it has been discussed already, but I couldn't find it,. Chapter 25:

And by similar logic: The words a wizard spoke, the wand movements, those weren't complicated enough of themselves to build up the spell effects from scratch - not the way that the three billion base pairs of human DNA actually were complicated enough to build a human body from scratch, not the way that computer programs took up thousands of bytes of data.

So the words and wand movements were just triggers, levers pulled on some hidden and more complex machine. Buttons, not blueprints.

And just like a computer program wouldn't compile if you made a single spelling error, the Source of Magic wouldn't respond to you unless you cast your spells in exactly the right way.

The chain of logic was inexorable.

And it led inevitably toward a single final conclusion.

The ancient forebears of the wizards, thousands of years earlier, had told the Source of Magic to only levitate things if you said...

'Wingardium Leviosa.'

No, not the ancient forebears. There are spells that sound "a lot older than Latin", and (at least in canon) there's a spell with incantation "point me" (Goblet of Fire, iirc).

So it looks like the spells haven't all been created at ancient times, but rather some spells have been created later. That is supported by McGonagall in Ch. 16, "people invent new Charms and Potions every year."

So, it seems there is some rather complicated way to invoke magic, and Charms present a shortcut that original discoverer of a spell has installed.

Why did it take more effort to cast the Alohomora spell, if it was just like pressing a button?

Probably because the spell only channels your magic, and there's a magical barrier that the locking spell has left, and that has to be overcome with magical strength. Or maybe it's more like pulling a lever than pressing a button. It's still efficient, but you still need some magical strength to perform the action.

Who'd been silly enough to build in a spell for Avada Kedavra that could only be cast using hatred?

As a safety mechanism. It prevents you from fooling around with the spell and killing somebody if you haven't actually meant it.

Why did wordless Transfiguration require you to make a complete mental separation between the concept of form and concept of material?

Since wordless Transfiguration doesn't have a word as a trigger, there needs to be a different mechanism for preventing accidental Transfigurationt. Going to some extra length mentally might be that safety mechanism

This is probably not the solution Harry's going to use in Chapter 81 (I'm writing this before it was posted), but a friend and I were discussing it and came up with a possible solution. I decided it would be much more fun as a piece of fanfanfiction rather than an abstract description, so here it is. I hope you have as much fun reading it as I did writing.

Chapter 81b: Alternate Solution

Beyond all panic and despair his mind began to search through every fact in its possession, recall everything it knew about Lucius Malfoy, about the Wizengamot, about the laws of magical Britain; his eyes looked at the rows of chairs, at every person and every thing within range of his vision, searching for any opportunity it could grasp -

And the start of an idea formed - not a plan, but a tiny fragment of one. He spelled out N-O-T-E on his fingers, and, as discretely as he could, drew a piece of paper out from his bag that he did not remember putting there. It read:

"Mess with time if you want!"

And then he heard a loud bang, and another while he was stuffing the note back in his bag, and he looked up to see that a circular piece had pushed out from the wall, (that wall that could've withstood a nuclear explosion), far in the back where no one had been looking. Heads turned in unison to look as four glowing, silver human shapes emerged from the three-foot diameter hole, and began walking down the aisle towards Hermione. No one in the room but Harry and Dumbledore suspected they were Patronuses.

Prime Minister Fudge should have been angry, that magical creatures would dare barge in; but for some reason he couldn't quite place, he was calm. Auror Gawain was too busy casting shield spells to acknowledge how scared he was. Harry had a pretty good idea where this was going, but decided that "confused" was the best expression to wear. Professor McGonagall nearly had a stroke. Lucius Malfoy's angry expression had vanished, leaving his face perfectly blank. His entire row had stood up, and drawn their wands. To his left, five wizards Harry didn't recognize were pointing at the human Patronuses; to his right, seven wizards pointed their wands at Dumbledore.

Lucius himself had his wand, and his gaze, fixed firmly on Harry. For a brief and accidental moment, the boy who thought he was a rock looked back.

Wands too numerous to count followed those glowing figures, as they walked down the aisle towards Hermione. Harry noticed that Fawkes had perched silently on her shoulder, and she was taking slow, deep breaths.

Behind each wand, a wizard thought that someone else ought to do something. A rare upside to the bystander effect, Harry would later note. For the time being, his mind was busy choreographing the movements of four invisible figures, who were definitely not bumping into each other. When the Patronuses had reached the bottom-most platform, where Hermione sat, they stopped, and looked up at Dumbledore's platform.

"Who dares interrupt these proceedings?" Dumbledore's voice boomed out. In fact, he was glad that they had been interrupted, and knew exactly who he was talking to; but as Chief Warlock, he had to express indignance, or else someone else would have gone and done it for him.

This better be good, Harry thought, because I won't be able to think of anything else once I've been anchored.

"We are the Guardians of Merlin", said the first Patronus, in Harry's best impression of a Scottish accent.

"In that case, I yield the floor to the Guardians of Merlin", said Dumbledore. "May I ask why you are here?"

"We were a safeguard created by Merlin, to protect the purity of the Wizengamot. In his wisdom, Merlin set down a list of especially vile deeds; should this assembly should decide to perform one, we awaken. And so we are here."

Lucius turned away from Harry, and towards the front. "Ridiculous. This is no different than the many other times we have punished murderers, and no ghosts or apparitions appeared then." He put a slight emphasis on "ghosts or apparitions". He had no idea what they really were, but there was ample precedent saying ghosts and apparitions weren't allowed to do things.

Harry wondered what lie his future self would tell. Then the second patronus spoke, in exactly the same voice as the first. "It is different, because sending this girl to Azkaban would satisfy the first requirement for a ritual!"

The murmurs stopped. Several members of the audience suddenly noticed the dementor in the room, on a level where they had not noticed it before. Professor McGonagall actually did have a stroke, but it was a small one, of a kind that could be fully repaired by magic later. For a moment, Dumbledore lost himself in his role and forgot that he was speaking to four copies of Harry Potter.

Five seconds passed before Dumbledore broke the silence. "Are you saying that this trial is part of a dark ritual?"

"Yes", said all four patronuses simultaneously, convincing several members of the assembly to abandon the idea that they were all controlled by one person. The figures were new, important, and mysterious. Hermione was no longer salient.

"Do you know who could be behind this?" Dumbledore asked.

Heads turned towards Lucius, who looked around and noted exactly whose heads they were, handling the sudden deluge of important information by recording only the ways in which it differed from what he would have expected. Lucius knew then, that he had to lose; not only was he facing four new and completely unknown pieces, pieces which had been powerful enough to carve a hole in the indestructible wall of the Wizengamot, his own role was looking altogether too suspicious. He looked left, met the eyes of his servant, August Stoessel, and sent a thought.

Two seats left, August stood up and shouted, "It must be Lord Voldemort!" The audience's attention shifted slightly. Lucius decided that four days later, Stoessel - Imperiused and falsely rumored to be a perfect occlumens - would confess to the whole thing, claiming (though no one would believe the last part) to have been Imperiused by Lord Voldemort himself.

Dumbledore looked very disturbed. Onlookers did not find this surprising, but they would have been surprised by the reason, if they knew. Dumbledore had just put the pieces together - Harry had performed an advanced plot, and time turned in spite of his time turner's locked shell, just as he must have done on the day Bellatrix Black broke out of Azkaban.

"Talk of dark rituals is unfit for discussion here", Dumbledore said, a little shakily. "If there are no objections, I believe we can suspend the previous vote and reconvene tomorrow morning, after the Ministry has had a chance to speak with these Guardians. We will vote whether to release or punish Hermione then, with fuller information."

Lucius did not object. He would have a whole day to plan his next move. Harry did not object. He would have a whole day to plan his next move.

The Guardians of Merlins left first, through the strange hole from which they had come. Then the Aurors left, taking Hermione, their patronuses, and the dementor, slightly smaller but still intact. Then the audience left, Harry among them, and he excused himself to go to the bathroom, where he anchored his time turner inside its shell like Quirrell had shown him, and spun the shell twice. Finally Dumbledore left; but he was only two steps out the door when he disillusioned himself, spun his time turner twice, and reentered.

Two hours earlier, an invisible Harry Potter was wandering around the Wizengamot building, first looking for his earlier self so he could place the "Mess with time if you want" note, then looking for the other side of the wall he had seen cut open. He found it in a secluded storeroom, with ten minutes to spare, set down a piece of paper and marked it with a single tally. Soon he was joined by another Harry, who had used his time turner only once, and another, and another. Rather than take off their invisibility cloaks, they announced their arrival by marking the paper with a second, third, and fourth tally.

Dumbledore watched invisibly from inside the Wizengamot chamber as four invisible Harry Potters used partial transfiguration to cut a hole in the wall. He watched invisibly as four Human Patronuses entered the room. And then an invisible Harry Potter bumped into the invisible Dumbledore, changing events from how they were meant to go; and the entire twisted tangle of time loops collapsed into a paradox and never was. Reality would take a different path, one in which Harry chose a simpler solution, one that did not require three things to all happen.

Maybe this is the wrong place to ask, but are there any other cool pieces of "edufiction" like HPMoR? I mean fiction where you can learn about science, economics or other topics just by reading the story, and thinking along with it.

There is lots of historic fiction material, so I'd like to exclude that genre from my question.

It's past the halfway point.