I remember that once Nearly Headless Nick told Harry that souls find a chance to come back to the world or go the other way (or something like this). Those who choose to come back or have an unfinished business come back. For example, Moaning Mertyl came back as a ghost to haunt those who bullied her.  Many people in the Wizarding World has some unfinished business. They can come to fulfill those. Death Eaters like Bellatrix could come to get revenge.  So why isn't the Wizarding World filled with ghosts?
In Harry Potter and the Sorcerer's Stone, Nearly-Headless Nick and some other ghosts can visit the Hogwarts students, but why can't other deceased people - such as Harry's parents?
How to create a sub array from another array in Java? Render result is completely blank I was thinking about something the other day (that is probably stupid), and thought this would be a good place to talk about it.  If someone wanted to draw its family tree over the last 1000 years, he'd write a binary tree with a depth of about 40 (counting 25 years on average between each generations). This tree would have 240 leaves, or about 1012 ancestors on the deeper level. That is obviously much more than the total world population and a stupid figure when you think about it.  The only explanation that I can think of is that a real genealogy tree must have "linked" branches at several levels that change the actual number of ancestors. Anyway, for an average person, how many ancestors would that make? Could one assume that all or nearly all of the persons that lived in its country or world region a 1000 years ago would be part of its ancestors? How can I insert a newline in a framebox? 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