This is hard to comprehend:
"It takes a million years for a photon moving at the speed of light to reach the sun's surface from its core."Explained on the basis of Thomson scattering: "The mean free path of a photon in the interior of the sun is about 2 centimeters. This is the average distance it travels in between bounces. If you compare this length to the radius of the sun, you see why it takes so long for the photons to escape."
Additional discussion and clarification of the "bouncing" in this thread.