Two Forms of Mathematical Beauty
quantamagazine.org
quantamagazine.org
[1]: https://link.springer.com/book/10.1007%2F978-3-662-57265-8
The beautiful irony of the once popular "god of the gaps" argument is that the gaps are continuing to widen toward infinitude each passing day. Each passing day we discover that "knowing" one thing reveals 9 more things we do not. How arrogant it would be to miss the awe-inspiring beauty, consistency, and self-sustaining processes that are everywhere, from mathematics to the physical and beyond.
I think that it depends on what you mean by 'core'. This is certainly the historical core of mathematics—where things started, and so around which all later developments have accreted—and I suspect it characterises a large part of most 'users'' interactions with mathematics, but I think that there are many mathematicians who would not describe your characterisation as the core of what they do professionally.
(It happens that I can't substantiate that even by a flimsy appeal to my own work, because there is a reasonable sense in which counting things is at the heart of my work (even though it's not combinatorics); but there are other fields that I think don't have that sort of connection informing their everyday work, even though it is of course always there historically.)
Those mathematicians are certainly doing something much more intellectually-challenging than counting things and measuring space, but I would argue that those basic activities represent the basic problems upon which most of the low-level math abstractions are built. "Serious" math is about operating at much higher abstraction levels, but it is not disconnected from those low-level foundations.
There's two kinds of mathematical beauty (maybe more, I'm making this up): concepts and proofs.
The other day I saw a proof of the minimax principle (about eigenvalues maximizing the Rayleigh coefficient) that used a variational problem over eigenfunctions. This is fairly "ugly" mathematics conceptwise, and there are simpler standard proofs, but this one made the top of my head pop out like that emoji. It explains why Rayleigh coefficients have that name, and links practical statistics/ML concerns (low-rank matrix approximation) to light and refraction.
https://www.dpmms.cam.ac.uk/~wtg10/2cultures.pdf
I especially like the Atiyah quote.
MINIO: How do you select a problem to study?
ATIYAH: I think that presupposes an answer. I don’t think that’s the way I work at all. Some people may sit back and say, “I want to solve this problem” and they sit down and say, “How do I solve this problem?” I don’t. I just move around in the mathematical waters, thinking about things, being curious, interested, talking to people, stirring up ideas; things emerge and I follow them up. Or I see something which connects up with something else I know about, and I try to put them together and things develop. I have practically never started off with any idea of what I’m going to be doing or where it’s going to go. I’m interested in mathematics; I talk, I learn, I discuss and then interesting questions simply emerge. I have never started off with a particular goal, except the goal of understanding mathematics.
I personally feel J.S. Bach would be a better metaphor here.