Unlike nukes, antimatter weapons can be made small enough yeild that you don't flatten the whole of hogwarts when you use one.

...but the amount of antimatter you'd use for that is very small indeed; about 0.000023 grams for an explosive yield equivalent to 1 ton of TNT, going by Wikipedia's numbers. I wouldn't put it past Quirrell to figure out a way to transmute quantities that small, but it'd be tricky; everything we've seen transmuted onscreen has been macroscopic.

Also, all the initial yield would be in the form of highly energetic gamma rays, so we'd likely be looking at something more like a hard radiation pulse than a bomb.

But, if the whole of Hogwarts stops playing altogether, perhaps because the school has been destroyed, then technically they have stopped playing with a

Harry's wish was for quidditch to be played without a snitch. Not playing quidditch doesn't fulfill the wish.

Assuming those are horcruxes, not like parts of the Philosopher's stone or something (but Horcruxes are more likely).

Totally-not-going-to-happen reason for Hogwarts to stop playing with a snitch: the "air" horcurx is a snitch. Dumbledore realizes that Snitches are dangerous, and bans touching them. (Much more likely: Mcgonagall becomes headmistress).

Well, what if even uber-time travel still has the paradox limitation. Harry figures out his becomus-goddus spell, and can go back in time arbitrarily far.

But if he mucks about with his own past in any way he doesn't remember he may unhappen his omnipotent ass. Moreover, this is true of almost all of history. Any mucking about that might prevent his timeline from making him invincible would be verboten.

So, what could he do? Not go back and tell himself everything, it would be a big gamble that his past self could consciously fake its way through the events of his own past timeline well enough to keep him in existence.

No, he goes back and Imperiuses himself, and only interferes in his life in the manners that he recognizes must have always been his future self.

So he: 1. Gives himself the strange sense of certainty that makes him believe in magic in the first chapter. 2. Whispers to himself on the train to meet Hermione Granger. 3. Steals Hermione's body (presumably what Harry did while alone with it was pointedly not observe it to leave a moment for future versions of himself to time travel in and steal it without creating a paradox)

I hope this isn't right, but I assign a relatively high plausibility that future Harry is running behind the scenes throughout the story.

Another offhand guess, he kills Volemort in the past via his own remembered dialog. Voldemort agrees (sarcastically) with Harry's mom that Harry is to live, she is to die, then requests she drop the wand and let him murder her. She doesn't, and he kills her. Then he goes to kill Harry. But I don't think "now drop the wand and let me murder you" was part of the deal.

My guess is he's unknowingly (possibly due to time travel Harry) under some magic that makes everything he says Unbreakable, and when he kills her and then goes to kill Harry he's killed by the oath enforcement mechanism, since he's agreed that she's to die and Harry is to live.

Re: Commuting time: as others have noted, there may be a big difference between driving vs. public transit. I take a bus and train to work, and when I moved from a 40 minute each way trip to a 1 hr 10 minute each way trip I noticed very little difference because I spend the time reading the newspaper and playing games, or sometimes napping. On really crowded days sometimes I will even take the train the wrong way one stop to the end of the line and get back on so I can have a seat. Though, I also work from home 2 days/wk, which helps a lot too.

Re: Guest rooms. In my neighborhood in the Boston suburbs, the price difference between otherwise comparable 3 and 4 bedroom houses is essentially 0 or very close to it. But let's say it was $20k. At current 30 yr mortgage rates that would be about $100/month, or 6-10 nights/yr in a hotel. So, do you have guests more often than that? My friends are scattered across the country, so for me I hit that number easily. And as others mentioned, at least some of that expenditure you would get back when you eventually sell the house. Also, there is value to having the extra closet space, or maybe the guest room doubles as an office (mine does), or you need an unused room to display the hideously ugly tchotchke grandma gave you.

Although the main point of this quote is valid (that sound policies rather than great men are the cause of good government), criticizing Lord of the Rings for having a “medieval philosophy” is a bit silly – it is like criticizing Johnny Cash for sounding “kind of country”. More so than an author of fiction, Tolkien was a scholar who focused much of his effort on studying medieval literature and translating that literature into modern English. Medieval literature was an inspiration and a major influence on his fiction. Of course the Lord of the Rings has a medieval philosophy; it was intended to have a medieval philosophy.

I really don't know. I did try and investigate why they didn't, for instance, use other stable distributions than the normal one (I've been told that these resulted in non-continuous prices, but I haven't found the proof of that). It might be conservatism - this is the model that works, that everyone uses, so why deviate?

Also, the model tends to be patched (see volatility smiles) rather than replaced.

Done!

a fourth tier, maybe with predictive value, where someone (a human being, not a Bayesian superintelligence) can draw on these observations to identify these leverage points and make informed decisions during them?

I.e. psychohistory.

I don't believe that it's strong evidence. It's more like a pointer to illustrate an idea. Furthermore the version of history that says that other countries copied the prussian school system is quite popular. Hegel also sometimes get cited for inventing history.