Page B19

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Why the Sky Is Blue

By Arlon Staywell
RICHMOND — The internet has answers to almost anything.  Many of the answers aren't quite right to some questions.  One such case has been till now the answer to why the sky is blue.  See the right answer forwith.
Color Generally
    We see things by the light that comes from them.  To see things that don't make their own light we must see light that bounces off them or more or less perfectly passes through them.
    There are four ways things can effect or not the light that hits them.  1) It might pass through uneffected as with "transparent" things.  2) It might be reflected or "bounced," for example toward our eyes.  3) It might be absorbed.  we won't "see" the light if it is absorbed, though we might perceive an area sending less light than other areas nearby.  4) It might be refracted or bent.
    Many things effect different colors of light in different ways.  Some might for example #2 reflect green light and #3 absorb all the other colors.  That's what a "green" object does.
    The color of something is the color of the light coming from it.
What Air Does
    Air consists of a variety of substances, mostly nitrogen and oxygen.  Because air is a gas there is considerable empty space between the molecules.
    The empty space between the molecules is #1 transparent.
    The molecules #2 reflect blue light and #3 absorb the other colors.
    In the day there is no significant #4 refraction.
    The direction of the reflection depends on where the light hits the molecules.  It will be a variety of directions from back toward the source to almost the same direction as before a glancing hit, and all the angles between.
The Answer
    The sky is blue because the air has a blue "tint" or "tinge."  We see the blue against the background of outer space because the blue light bouncing off the molecules in air drowns out the faint light from stars.  Of course the stars are still there.  The sun and moon do not appear blue because the much brighter light from them passing through the empty space in the air drowns out the light reflected off the molecules in it.
Why Does Air Seem Clear?
    Air seems clear for the same reason water seems clear.  In quantities too small there isn't enough color added to the light mostly passing through.  Although water does not have the empty space air does, it is mostly transparent as even solids can be.  Even looking through great quantities of air, for example at the white sands of a distant desert, the blue of the air will be drowned out by the light coming from the other thing beyond it.
Why Are Clouds White?
    Although water is blue the surface of water has a reflective quality that bounces all colors a little bit.  That's how the still surface of a pool acts a bit like a mirror.  The tiny droplets of water in clouds are still much larger than molecules, for example in water vapor, and present a surface with that reflective quality.  The countless thousands of tiny droplets don't act like the smooth surface of a pond mirror but more like the hairs of a polar bear that are actually clear, not white.
Why Are Sunsets Red?
    This question is the one often answered wrong on many websites.  They claim that it is because at sunset the light must travel through much more air and that removes the blue light from it.  At sunset the light does indeed pass through far more air, but that removes more red than blue light.  Remember that air absorbs red light.  Sunsets are red because the angle at which the light strikes the atmosphere is sharp and that causes #4 refraction.  Just as a prism bends the different colors of light at slightly different angles, so does the atmosphere.  Typically this means that the clouds will be hit by the red light.  Of course sunsets can have a variety of colors caused by the various combinations of absorption, reflection and refraction caused by the various arrangements of air and various concentrations of water at various heights.
    It is not the quantity of air but the angle at which the sun hits it that causes red sunsets.

How cool is that?

© MMX by Arlon Ryan Staywell

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