Over at Starts With A Bang, Jillian Scudder of Astroquizzical takes on a doozy of a question:
If a photon of light escapes from a star, when it hits another star, does it get absorbed and have to complete another cycle before it can escape again?
After all, it takes (on average) over 100,000 years for a photon created in a star’s core to find its way to the surface and exit.
But what about the photons — much lower energy than the gamma rays the core generates — that hit the surface? Will they simply be absorbed and re-emitted outward, the way the Earth’s surface absorbs and re-radiates sunlight? Or will they have a good chance of migrating into the core again, where they need to wait, you know, some 100,000+ years before they can escape into the Universe once again? Random walks, after all, can take you an awfully long time to get you to your destination.