A thread on any forum... :
"Could someone please explain why is the sky blue?"
"Ah; but it isn't really blue."
"Quite; it's not nearly as simple as that."
"Don't forget sunsets."
"And then there's the whole issue of rain."
"Quite. Then it's not blue at all."
"Of course it is. It's only at ground-level that it appears not to be."
"But of course the higher you go it starts to go black."
"Why is that?"
"Well it sometimes appears
blue because it's reflecting the sky."
"Oh sorry. I thought he asked why is the sea
"I think pollution is a terrible thing. Blue Sky? Have you ever been to India?"
"Well that depends which part of India you're talking about."
"Quite so. I was in the Himalayan foothills once and we had blue sky all week."
"Hang on. he only asked for an explanation of 'blue sky'".
"But it's not nearly as simple as that. If you don't give the full explanation he'll never understand about refraction, water vapour, atmospheric pressure, high-altitude dust and all the other vital aspects."
"On the subject of high-altitude dust, I seem to recall..."
"No that's not right. What's your source?"
The O/P: "I had no idea it was so complicated. I think I'll take up knitting instead."
There's nothing so simple that you can't make it complicated if you put your mind to it.
[Climbs off hobby-horse]
I'm done on this... taking up knitting...