Suppose that I put in the outer space (where gravity from other bodies is negligible) a large, perfectly round sphere totally filled with water. At the bottom (even though "bottom" doesn't make much sense in the deep space) of the sphere there are several marbles, all touching each other.
If I make rotate the sphere, all marbles should stay exactly where they are. Right? Is that true regardless of the force that I apply? And what happens, instead, if I strongly shake the sphere?