Find curl v where v is the gravitation field given in Example 2.
Suppose that the origin of a coordinate system is at the center of the earth and R is its radius. Denote by g the acceleration due to gravity at the surface of the earth. For points p in R3 let r be the vector having as a representative, and set r = |r|. From classical physics it is known that the vector field of force due to gravity, denoted v(p) and called the gravitational field of the earth, is given approximately by