Like any thoughtful man, I'm getting dumber as I get older. Things that I thought I understood years ago, I now realize I don't understand at all. For example, I thought I knew why the sky is blue.
Here's the way I had it: different frequencies of light (or any electromagnetic wave) react differently to various kinds of matter. This is why radio waves will go through the wall of your house, but visible light won't. In particular, when sunlight goes through the atoms of the air, long red light just slides right through, but short blue light often bounces off.
So when you look up into the sky on a glorious fall morning such as yesterday's, which you can do if you're unemployed like me and can spend the morning reading in the backyard, the red, yellow and green colors of the sunlight shoot by high overhead and keep on going, so I don't see them. The blue colors bounce off the air and some of those blue rays bounce down into my eyes, giving the sky that beautiful color.
Well and good. This theory (a) explains the data, (b) doesn't conflict with anything else I know about light or skies, and (c) doesn't sound any crazier than lots of other stuff I believe.
Last night I was reading Robert Herrick's The Master of the Inn (a swell old book from the early 1900's, if you can find it) and he had a fine description of the blue New England hills receding into the distance. I've seen this effect myself and I imagine you have: the distant hills turn into blue-gray outlines.
Now my Inner Wisenheimer speaks up. "You see the hills by sunlight which reflects from the side of the hill to your eyes," he says in that irritating tone. "The reflected light travels through the air. The longer frequencies should go straight through the air to you, but the shorter frequencies should be bounced to the side. That is, distant hills should appear more red, not more blue. Hah? How about that, Cheese-for-brains?"
Here's another one: think of a piece of blue glass such as the old-fashioned drinking glasses I used to have. If you look through them, the colors drop out of the world and everything is shades of blue, because the glass filters out the other frequencies and passes only the blue light through. Seems simple enough, right?
But when you put the drinking glass on the shelf, you can see that it's blue. You're seeing it by reflected light, which means that it is returning the blue frequencies and absorbing or scattering the others. Isn't that the exact opposite of the transmission filter effect? Shouldn't the glass appear any other color except blue?
Your comments will be appreciated, if you've got time to spare for an old man who's a few ants short of a picnic.