times the enclosed mass if the source is inside, and zero if the source is outside.
Arnold explores the property of the gravitational field (or any Ángulo sólido – Arnold 2.2.3
force) where the potential is related to the surface area of a unit sphere "covered" by an object when viewed from a point. The solid angle Ωcap omega subtended by a surface at a point is defined as the area of the projection of onto the unit sphere centered at Mathematically, for a small surface element at a distance , the differential solid angle times the enclosed mass if the source is
that enters the volume must also leave it. The "entry" and "exit" patches of the surface subtend the same solid angle but have opposite flux signs (due to the orientation of the normal vector). : The net solid angle (and thus net flux) is 4. Physical Implications The "entry" and "exit" patches of the surface