Rob Naylor:
Grandmother to suck eggs! My first degree (since people are bandying qualifications about on this thread) is in Astrophysics to I'm perfectly aware of all that. In fact, the full comment at the end of "Eclipse" was: "There is no dark side in the moon, really. As a matter of fact, it's all dark. The only thing that makes it look light is the sun." But you can't hear the final sentence! It was one of the answers solicited by the band from people hanging around the studio who were given various questions on flash cards to which they were asked to give spontaneous answers. This one was from the Abbey Road Studios doorman Jerry O'Driscoll and IMO in its full version shows a very reasonable level of knowledge from a "lay" person giving an off-the-cuff answer to an unexpected question.

Being VERY pedantic, the full comment would have been more accurate if it had been: "There is no dark side in the moon, really. As a matter of fact, it's all dark. The only thing that makes it look light is the sun, and a bit of reflected light from the earth, but since that originated as sunlight anyway, we can still accurately say that the only thing that makes it look light is the sun"
Thank you for that 'clarification', and i'm glad to see that you have an astrophysics degree to (although I can't see what the 'to' relates to).
Unfortunately I didn't benefit from higher education, so my descriptions & understandings may seem simplistic.

I take it from your description that (excluding a small amount of light pollution) the earth should also be considered as being 'dark'.
I shall have to be careful not to trip over when walking about in daylight!
Does 'dark' equate to non-luminescent in the lingo af astrophysicists? If so then presumably 'light' means illuminated other than by external sources.

I think I need a new dictionary.

But thanks for the 'illumination'.