The other is this:
Oh, the dooblydoo:
Harry Potter, Aunt Marge and the Harry Potter series, with all associated ideas, depicted events and settings, along with the Prisoner of Azkaban, are copyright J K Rowling. The books are published by Bloomsbury, the film series produced by Warner Bros. No infringement intended.
J K Rowling's website: http://www.jkrowling.co.uk/
OK, now this is about the physics of Aunt Marge. Is it physically possible for someone to be inflated to the point of being lighter than air? Well, obviously not - it would be magic. However, if she were infinitely elastic, she would have to be over five metres in diameter. This also means that in order to be lifted by a hydrogen balloon, that would have to be at least that size, ignoring the mass of hydrogen involved.
This is based on two assumptions: Pam Ferris as Aunt Marge and the idea that Aunt Marge has a BMI of about 35, i.e. that she weighs 90 kg. Rather surprisingly, Harris tweed is quite a suitable fabric for inflation because it has a lot of give in it due to the twill weave, which skips fibres and is therefore quite loose and open compared to tabby weave.
The minister for magic claims that she was punctured and her memory altered. This seems to imply that she didn't pop but deflated relatively gracefully.
As you can see from my diagram, the whole idea is a bit far-fetched, but maybe a bit of Wingardium Leviosa was involved.
This is of course almost entirely about someone else's intellectual property, but then there's a lot of that on YouTube. I've stuck in the necessary acknowledgements, so if anything this acts as free publicity for them, hence the links to Pottermore and the like.
Some maths were involved, and maybe i should've included more of that. Incidentally, this video has confirmed my suspicions about the inherent bias of Wikipedia. Here's a still from the video:
I am unsurprisingly by no means an expert on knitting, though i have a lot of respect for it. When i look at Wikipedia articles on textiles, i can't really comment on whether they're accurate or have enough detail. I also suspect that most people who edit Wikipedia are not very into knitting. As a result, although i can't tell i would be surprised if there weren't subjects such as knitting which are either highly biassed or just plain missing. I can sometimes see this happening, for instance with herbalism and home ed. Also, the thing about Wikipedia is that once you submit something to it, it gets copied all over the web and then, when you look for confirmation, that will at first appear to be copious until you realise that all those references may have been made after the Wikipedia information was added and you have warped the very fabric of the Universe and messed with the collective mind of Homo sapiens instead of checking your sources. Hence it's probably quite important to contribute accurate information about knitting to Wikipedia.
The irony of all this is that looms and knitting machines share a common ancestor with computers, and it's the nerds who are into the latter, with the result that there's rather little on the former on Wikipedia.
OK. Now there's this diagram, which is a bit naff: