Katrina Hunter, age 11, of Bountiful, Utah
Why is there never a rainbow at noon?
When you give just a glance to the rainbow, it looks like a streak of dazzling colors spilled helter‑skelter from some heavenly paint box. A closer look shows that the colors are arranged in bands and a little study shows that the bands of color are arranged in a special order. In a single rainbow, the band at the top is red. Below it is a band of shimmering orange, then a band of yellow which blends into a band of glimmering green. Then comes a band of light blue blending into a band of deep indigo blue and finally, on the inside of the bow, a band of velvety violet.
The flowery colors of the rainbow are actually the colors hidden in every sunbeam. We do not see the colors in sunlight or ordinary white light, but there are certain tricks by which the dazzling skein of colors can be broken apart. Then we see the spectrum. The trick can be done by a prism, a glass rod in the shape of a long triangle,. It can be done by oil on a puddle. In both cases the rainbow colors of light are separated into bands and we see the spectrum of white light.
The most dazzling spectrum appears when the gleaming rainbow hoops over the sky. Mother Nature does this razzle‑dazzle trick with a special stage, special lighting and millions of mirrors. And for the trick to come off perfectly, every stage prop must be in its proper place. The back of the stage must have a dark curtain, the mirrors must be exactly between the dark background and the stage lighting.
The curtain, of course, is a dark rain cloud and the mirrors are millions of falling raindrops. The stage lighting is the beaming face of the sun„ The raindrops must fall between the cloud and the sunbeams coming from the sun.
The sunbeams, then, must come slanting in and this only can happen when the sun is low in the sky. At high noon, the sunbeams come from high overhead. Sometimes in an airplane, the sunbeams make a rainbow on the clouds below us, even at high noon. This also can happen when you are above the clouds on a mountain top.
But from the flat ground or on the sea, the rainbow appears only when the sun is in the eastern or western part of the sky. The dark cloud with its tumbling raindrops must be to the opposite side of the sky where the slanting sunbeams can strike the millions of falling mirrors. In the afternoon or evening, the rainbow is in the eastern part of the sky. The morning rainbow glimmers in the western part of the sky.
Most of North America is in the belt of the prevailing westerly winds and much of our weather travels from the west towards the east. A rainbow, then, may give us some weather information. The morning rainbow may mean that rainy clouds are on their way from the west. The evening rainbow may mean that the clouds have passed overhead and clear skies are on the way.