I'm doing research on why some galaxies and other phenomenon like Saturn's rings are flat. There seems to be two answers. Here they are in shortened form: 1) When the galaxy is forming, there is some net angular momentum in some direction.Over time, all particles with an angular momentum pointing at some tilted direction will collide with other such particles, and will either be destroyed, ejected, or their tilts will be less extreme (Although I must admit I don't get who this will flatten it out, it seems to me this will only create a system where most particles are moving in the same direction). This appears to be the more popular explanation. 2) When spheres rotate, they are flattened along their axis of rotation due to the centrifugal force being stronger perpendicular to the axis of rotation. This is why the Earth is flattened a little bit. ICRAR in 2014 found that the faster a galaxy rotates, the thinner/flatter they are, which goes well with this explanation. I'm confused which explanation is correct, or if both are - and if both, how they are related. Thanks for any help.