In vector calculus, divergence is an operator that measures the magnitude of a vector field's source or sink at a given point, in terms of a signed scalar. For example, consider air as it's heated or cooled. The relevant vector field for this example is the velocity of the moving air at a point. If air is heated in a region it'll expand in all directions such that the velocity field points outward from that region. Therefore the divergence of the velocity field in that region would have a posit… (More on Divergence)