"So, tell me again, why is the sky blue?" the little boy asked for what seemed like the millionth time.

"Well," his grandpa replied, "it has to do with molecules and light. You see, the blue light waves get scattered and radiated in all sorts of different directions. So that's what you see. The other colors don't get scattered; they just shoot right through." And here the grandpa paused to let it sink in. Then he decided to add a name because people remember facts better when they can add a name. So he continued, "An English scientist named John Rayleigh discovered why the sky is blue about 140 years ago." The grandpa stopped to see how things were going: "Does that make sense to you?"

"Well, a little bit, sure," said the little boy.

Then there was a long pause.

"But can I just tell my little sister that tiny blue fairies fly around in the sky real fast so we see the blue of them whizzing by?" asked the little boy somewhat hesitantly.

"Yeah," said the grandpa, "that's a good explanation too."