Q:
A: The natural order of things is to assume a spherical or circular shape. Take bubbles, for example. Or drops of oil in water. Spheres are stable, symmetrical in any direction, and are the result of a gravitational pull from particles. Even atoms have a naturally rounded shape. Mind you, this comes with some exceptions. For instance, Jupiter is a rather flattened sphere (imagine a yoga ball with someone barely sitting on it) because it spins so fast, so it kinda bulges in the middle. Anyway, look at our solar system: circular. The planets and stars: circular. Spheres are a very stable shape, therefore, over time, most structures assume a rounded form (aside from crystallization, which relies on certain molecular formations).