1. The problem statement, all variables and given/known data While solving a question on gravitation I had to consider a very thin spherical layer of a uniformly dense sphere. It's written in the solution that : "Then the considered layer is attracted to the part of the sphere lying within it (outer part doesn't act on the layer) 2. Relevant equations 3. The attempt at a solution I have problem in the bold part. Why wont the upper part not attract the layer? Why only the inner layer will do so?