I was curious as to how planetary type spherical bodies form. Specifically, I was curious as to how the gravity affects the nebulous particles moving within themselves just prior to a solid planetary body forming. Is it not true that gravity is essentially zero in the center of a planetary body, since there is just as much mass in all directions? Prior to the creation of a planetary body, does the circular movement of the particles not create a centripetal force that pulls the particles further from the center at a greater force as one moves towards the outside, where the particles are spinning more quickly? So if the center of the pre-spherical body is essentially zero in aggregate gravity but has a stronger pull from a centripetal force, would it not reason to think that this centripetal force would hollow out the particles just outside the zero-gravity center until a critical maximum is reached where the force of gravity pulling the outside particle on themselves is cancelled perfectly with the centripetal force created from the spin. Essentially the end result may be a more hollow spherical form that does not collapse due to the same principle that a roman arch does not collapse. :surprised If anyone has any input to these questions, I would greatly appreciate it, since this information is not easily accessible.