If you're finding this discussion interesting, you might also enjoy the most recent
Irregular Webcomic podcast (The word "podcast" is a second link.) You can download Episode #4, or read the transcript.
This is one of my favorite Webcomics. The author is a professional astrophysicist, and is quite good at explaining things in layman's terms. Podcast #4 explains why the night sky is black, which turns out to be relevant to this thread.