Question: This question is for all the novels. How are all the schools in the wizarding world kept hidden from the muggle world? Surely if a plane were to fly over Hogwarts, people would be shocked at seeing people flying around on broomsticks and using magic.
Question: Has it ever been explained what happens to a wizard/witch if they don't repay a life debt? Harry should owe one to Snape after Snape rescues him from Quirrell's curse during the Quidditch game, but he never does throughout the series.
Question: I heard that Quirrell was the muggle studies teacher before this year. So after he took defense against the dark arts, why not give muggle studies to Arthur Weasley?
Question: The night when Harry is given to the Dursleys takes place in 1981. McGonagall and Dumbledore each say something about "for eleven years", so they are referring to the year 1970. What happened that year? I know from the sixth book that Voldemort had been around and gathering followers since way before then; he had some followers when he was 28 and he visited Hogwarts to apply for teaching Defense Against the Dark Arts.
Question: This question is actually about all of the books. Is a "double" class twice as long as normal, or does it contain twice as many students?
Question: Has JK Rowling said what happened to James Potter's parents and Lily's? They were only 21 when Voldemort killed them, and most people of that age still have living parents.
Question: Why did Snape have Filch treat his wounds from the three-headed dog? Why not go to Madam Pomfrey in the hospital wing, considering that Snape wasn't really doing anything wrong after all?
Question: Do magical folk generally live longer than Muggles? Considering that Minerva is described as having black hair, even though she is old enough to have taught Harry's parents, and Dumbledore is more than one hundred years old (according to the Harry Potter Wiki).
Question: Why did Professor Quirrell really have the garlic in his classroom? I know that some people thought he was afraid of a vampire who wanted revenge. Since he was serving Voldemort, however, it seems that a vampire would not be a serious concern for him.
Question: What did Harry and his friends come across when they were trying to escape from Filch?