Up to this point, we have been considering the Sun in terms of material which can be described reliably by the laws of “ordinary” gas dynamics and radiative transfer. This has been sufficient to allow us to describe in some detail the overall structure of the Sun, including radial profiles of pressure, temperature and density from the center all the way to the surface. But the very concept of a radial profile incorporates the assumption that the profile is the same in all directions, i.e., the material is spherically symmetric. This is certainly an adequate assumption deep in the interior of the Sun.