You know the old joke, right?
The Apollo 11 astronauts discovered a restaurant on the moon, not far from the landing site. At debrief they were asked about the place, they said the food was great, but it had no atmosphere...
I mention this because earth's sky is blue because we HAVE an atmosphere...something I learned around the age of 4 while watching the Apollo coverage, and also Star Trek reruns where Mr. Spock deftly explained atmosphere, and how its composition of gases defines the color.
So for the slow person on this thread, on earth the night sky is black, but on the moon the sky is ALWAYS black due to no atmosphere. This is what they call an obvious fact, but someone can't figure this out.