> a perfect circle has never been observed in the universe Yeah, that's not true. Many things in the universe have perfectly spherical or spheroid shapes, cros

> a perfect circle has never been observed in the universe Yeah, that's not true. Many things in the universe have perfectly spherical or spheroid shapes, cross sections, or propagation patterns, like black holes or isotropic EM emissions or (more abstractly) light cones. Pi is baked into the laws of physics in many locations as a consequence of the geometric behavior of our spacetime. It would also be baked into a lot of other plausible spacetimes. It's hard to quantify exactly what causes it to come up so much, but it's probably the fact that our universe is locally Euclidean and therefore uses the L2-norm for distance, which gives rise to circles/spheres as the unit shape and the extrema of a number of optimization problems.