"Chuck, I recently spent a couple weeks back in Cincinnati."
"Great town, Bob."
"Sure is. But as we were driving in, I happened to look at the sky, and it was a color I have never seen before, Chuck. I would call it a sort of a purply-greenish glassy pearl."
"Sounds pretty. Your point, Bob?"
"Well Chuck, when I was a kid back there, you could look at the sky and it was always some color you might expect the sky to be. And now it's not. So my point is, Chuck, exactly when did this happen?"