I have a few hobbies, some weird and some not.
When I was a kid, I was designing stuff left and right: Buildings, trains, sailboats, space ships and space stations. Other kids would play with G.I. Joe action figures; I'd be designing my 27th dream house. Now I'm in the architecture business and I design buildings for a living, so I guess I can't really call it a hobby anymore. It's probably lost a little bit of its novelty since I started doing it for a living, but I still enjoy it most of the time, and I can't imagine doing anything else.
In a somewhat related vein, I'm fascinated by how cities develop and grow, urban infrastructure, and comparisons between cities. Give me a chance, and I'll bore you to death about the symbiotic relationship between New York and Chicago. I also love trains, especially electric passenger trains such as subways. I love learning about the trains themselves, as well as the infrastructure that supports them. I can identify every class of subway car on the NYC subway system, and I can tell you all about the differences between the former IRT, BMT, and IND systems. Always the life of the party!
(As you might imagine, New York City is pretty much like a huge playground for me.
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Also, I'm not sure if I would classify it as a hobby or not, but I've always had a strong fascination with people who have unique physical characteristics, such as amputees or people with webbed toes. I don't have any such deformities myself, but a few of my closest friends are amputees who accept my fascination, and my biggest romantic crushes have all been on women with one or more missing limbs.
I've often thought about why I have this particular quirk, and I'm sure it has something to do with the fact that both Aspies and people with visible deformities can often feel isolated from the rest of society. There's actually a small internet subculture of people who share this fascination, and I'd be willing to get that a large percentage of them are Aspies. No doubt there's a Ph.D. dissertation in there somewhere.
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I've lost my faith in nihilism.