As GP said, continuum mechanics is often used for physics research. While not the Truth, the models can often be accurate. My own research involving transport in the quantum domain utilized some models from continuum mechanics.

(I didn't introduce it - it was already being used).

Physics: research, theorize

Engineering: practical implementation

That’s how it goes in my brain. It’s physics until we can build it reliably, then it’s engineering.

You could say that about a lot of topics. Heck you could say that chemistry is just an emergent phenomenon of physics.

The benefit of taking such a class or reading such a textbook is that these things have been studied extensively, we have good models for them, and it is useful to know because people are still doing fundamental research on it to this day or working on phenomena that are closely related.

Reminds me of a student sketch from my days in nerd school, parodying Star Trek. A student dressed as one of the physics professors demonstrated that FTL travel was impossible, causing the Enterprise’s warp drives to stop functioning. It was fixed when Scotty said, “Wait, I’m an engineer: I don’t need to understand physics!”

> Shouldn’t physics focus much more on the underlying micro states and micro processes than the emergent phenomena? Obviously there needs to be a transition, but at some point you go from physics to engineering.

1. The boundaries between disciplines are where they are in part by historical accident, and in part because that's what the people working in them find useful - there is no actual fact of the matter.

2. We don't actually know the underlying microprocesses of anything. Effective theories are all we have, and there's no fundamental difference between an effective theory for the vacuum (if it is a vacuum) and one for, say, the bulk of a semiconductor.

> there is no actual fact of the matter.

This is true of all categories, so not a helpful comment. I suspect someone has a good enough definition.