[ordu]

> An orthogonal question is what makes sense as a measure of complexity.

I don't know, but number of parts doesn't seem good. I feel that complexity should be measured in bits, but how to tie it with something real idk. Maybe the amount of knowledge needed to reproduce the machine? It is hard to measure though, because knowledge in people heads can't me measured precisely, we can estimate it but it will be a very rough estimate.

But the knowledge by itself is not enough, because there difficulties when producing that pure knowledge can't solve, they need a specialized equipment or source materials, and arguably it adds to a complexity too.

Or we can try from completely different angle, how about the reaction of a machine to small perturbations? Like if I unscrew this bolt, how long it will take for a machine to explode? xD

I mean, I'm not an engineer really, but I have experience as a software developer, and subjectively complexity of a code is when you can't predict at all what will happen if you change this line of code. Maybe it can be taken as a basis for a measure?