Seems like the universe was opaque for 380k years, and then suddenly nuclei capture electrons and there's an almighty flash, in all directions. By this time the universe is what, a million light-years in diameter, or less? Seems like the light from the last scattering surface would have gone by us already. Why can we still see it as though the surface were sitting there like a star 13.4B years ago? Is there a "Cosmic Microwave Background for Dummies" book or link?