The rabbit hole thread: what deep interest are you currently inside?

[Inland Aidan]

Not a general interest, a specific rabbit hole. The thing you have been reading about or watching or doing for the last few weeks that started from something small and has expanded into a whole new area you did not expect to care about.

These are often the most interesting conversations because the rabbit holes people fall into say something specific about them and the connections they find unexpected. What's yours right now?

[Nina26]

The history of the London Underground. Started from reading something about a specific station and now I have three books and a detailed knowledge of the 1930s design programme and why the roundel looks the way it does.

[Red Builder]

Medieval Islamic mathematics. Fell in there from a throwaway reference in something else and discovered a whole tradition of algebra and geometry that predates what I was taught as the origin of these fields by several centuries.