Having had a bunch of CT and MRI scans made me think of something I'd been thinking about, on-and-off, for years: How does tomography actually work? You scan an object by seeing how much it absorbs from a bunch of angles, and somehow use that to reconstruct the original object's structure - how does this magic work?
The obvious way to find out would be to read up on the subject. I decided to do something a little different, and try to reinvent it without reading up the existing theory. So, that's what I did - with the results up at https://github.com/simon-frankau/rediscovering-tomography.
Reinventing areas of maths is... interesting. As well as working out how it all works in theory, making it work practically is full of fiddly tweaking - I'm very much an amateur at numerical coding - but it was a fun project. If you want to know more, go follow that link!