Physics is about describing the fundamental behaviour of reality, and so it is rather natural to think of the work as a process of discovering how to best describe it.
What maths is, is harder to say. Certainly it starts by just picking a set of rules, thus inventing a new thing with some properties.
But, much like how a developer might ”invent” a program that solves some problem, but only ”discover” the bugs they wrote, so the mathematician too must spend a lot of time working with their newly created object to ”discover” what it really does.
I'm no mathematician though, so my understanding may not be perfect.
Edit: FWIW, Wikipedia uses the verb "developed" for calculus:
> Infinitesimal calculus was developed independently in the late 17th century by Isaac Newton and Gottfried Wilhelm Leibniz...
But surely, pi exists as a concept in nature and is something that we found, and didn't come up with? Confusing stuff.
Yes, the closer you look, the more difficult it gets.
It's more fundamental than that. It would be the same value in any universe.
You don't need circles, or Euclidean space, to discover Pi. It arises in all sorts of pure mathematics that have no direct connection to physical circles.
That said I suspect you are right that we gave a name to it because it comes up so obviously in our experience.