Ask HN: How to Find a Side Project?

I've found myself in an interesting situation. 18yo. I'm interested in astronomy, sports, (Hardcore)History, language learning, and piano. Generally a curious human.

I've formed cool projects in the past year. But lately, I've expanded my areas of interest rather than started a new side project, and I'm bouncing from one to another(from running to playing the piano, etc.). It's like walking in the park versus embarking on an adventure.

I like my day-to-day. I only think an adventure would be great for the mix. How do you find one?