I know that gravitational potential due to uniform sherical shell at a point outside the shell is equivalent to the potential due to particle of same mass situated at the centre and got proof here http://m.sparknotes.com/physics/gravitation/potential/section3.rhtml. But I was looking for more intuitive proof. Can anyone help me? It really bother me.
Short version is that the integral of the gravitational flux over the surface of some volume depends only on the enclosed mass. If you have a spherically symmetric mass distribution and consider the surface of a concentric spherical volume then the answer drops out in a couple of lines (hint: in this case, ##\vec g.d\vec A=gdA##).