Why does a stable galaxy or planetary body create discs shapes rather than ball shapes? Saturn seems a prime example of this, phenomena, why would gravity seemingly work on only one plain?

 

 

Why does a stable galaxy or planetary body create discs shapes rather than ball shapes? Saturn seems a prime example of this, phenomena, why would gravity seemingly work on only one plain?

 

Its not that gravity only works on one plane, it that these bodies had some net rotation when they formed. This tends to flatten its shape out so that when moons and rings form they tend to do so in the plane of rotation. This is aided by the fact that anything that tries to orbit at an angle to this plane finds itself constantly crossing the orbits of the majority of objects at an angle. The constant interactions tend to either cause it to eventually join suit or be ejected from the system.

Pretty much the same reason why spinning a ball of dough spreads it out, I think.