“Spheres are indeed fertile theoretical tools that help us gain insight into all manner of astrophysical problems. But one should not be a sphere-zealot. I am reminded of the half-serious joke about how to increase milk production on a farm: An expert in animal husbandry might say, “Consider the role of the cow’s diet... ” An engineer might say, “Consider the design of the milking machines... ” But it’s the astrophysicist who says, “Consider a spherical cow...”
