I used to do some fossil digging in an abandoned brick factory, where people have open access to layers and layers of shale rock rich of invertebrate animals. I thought it could be a useful hobby to teach my son about Geology in general and get him moving. Sadly I dropped it when he was 3 because I really did not have the time and energy to pursuit it frequently. I also thought about attending a few Geology classes in local universities but that probably needs to wait until he grows up.

The other hobby I have is to read the source code of legacy kernels such as Linux kernel 1.0, figure out a very early version of a component (e.g. VFS) and tried to trace how it evolves. I completed the MIT xv6 labs for preparation and just started this journey. Not sure what I can get from it, but it is fun to figure out things -- AND I can label myself as a "kernel programmer" to give myself a bit of self-recognition.