I used to wrench on tugboats. I got fairly good with imperial over the course of 5 years (we didn’t have enough metric parts for me to get used to them). US car mechanics really live in a mixed, but primarily metric world these days.

I can’t speak for everyone, but toward the end of my time I began to think of the bolts with far more context than in the beginning. They became less similar, seeming more like individual components than different sizes of the same component.

It’s really similar to learning anything. I just spent a few evenings making photos of the southern sky, something I’ve never really studied. At first, it all looked like random dots, but by the third night, I started seeing them a little differently. The shapes started to have their place.

I can only imagine what it must be like for physicists. When I see even the simplest modern equation, it’s completely devoid of meaning. But, there are these people that can look at a whole chalkboard and pick out the one function that’s out of place. It’s almost a craft, beyond simply understanding the mathematics.