Why does Pi show up in so many diverse equations if it’s only related to a circle?

Question

Is Pi more than just a ratio for circles? Is there a easy way to understand the universality of Pi?

In: 1018

Answer 1

One big reason is that the universe is essentially radially symmetric. In the grand scheme of things, forces will act in all directions without preference. This behavior favors spheres as the ideal shape in the universe to balance against forces.