This section is from the "The New Student's Reference Work Volume 5: How And Why Stories" by Elinor Atkinson.
You can't imagine a rainbow-colored sky!
Oh, yes, you can. Haven't you seen the brilliant colors of sunset? When the sun is above us, at noon, the light rays come straight down to us, or at a slight slant through the atmosphere. Then we get the reflection of the blue rays, only. But when the light comes to us in level lines along the surface of the earth at sunset, the rays pass through a thicker layer of smoke and dust. From more impurities of more varied sizes and greater densities, the red and yellow rays are reflected, as well as the blue. Some dust particles combine reflections, giving us green, orange and violet lights. At sunrise the same thing happens, but, for some reason, the colors of dawn are usually more delicate and transparent than at twilight.
Sometimes the amount of dust in the air is greater than at others. Volcanoes have been known to throw columns of ashes or volcanic dust into the sky as high as two miles. This dust is carried on the upper currents of air to great distances. It is even thought that it sometimes forms a belt entirely around the earth. After days and weeks all this great volume of volcanic dust settles, or is washed out of the air by rain. But while it is in the air we have a series of very fine sunsets and sunrises.