David Lowe, age 13, of Elizabethtown, Ky.,
Why are the sky and the sea blue?
Rusty red is the color of Mars and our neighboring planet on the other side is golden Venus. If we take a plane trip around the earth, we fly under the blue roof of the sky and below us most of the globe is covered with the blue‑green ocean. The land masses are tinted with tones of brown and large areas are clothed with green foliage embroidered with rainbow colored flowers ‑ but in the main, our's is a planet of heavenly blue.
The sun and the stars shine with the light from their own fiery furnaces. Some are red hot, others‑ hot, enough to glovi‑with orange and some are white hot. This is one reason why we can detect different colors in the stars. But this does not explain the different colors of the cold planets ‑ the redness of Mars or the gold of Venus. It does not explain the countless colors of our variegated earth, the blue of the sky and the sea.
Our days are lit by the light of the star which is our sun, Out in space, it is white, or invisible, light. It breaks apart into a multitude of colors only when it strikes some object made of matter. This matter may be the solid surface of Mars, the dense atmosphere above Venus, the air around the world, our seas and the countless different substances on the land. Each different substance, whether it is gas, liquid or solid, steals its own color from the white light which comes from the sun.
The air above our heads is made from tiny, free‑floating particles of
gas. These atoms, ions and molecules steal the blue rays from the sunbeams and scatter them over the sky. Each color hidden in white light travels on its own wave length, and a wave length is a pulse of energy,, up and down like a wobbly line.
The blue rays have the shortest wave lengths, short enough to be trapped by the particles of air in the atmosphere. This is why the sky looks blue, Water, like glass, tends to let through all the rainbow colors of white light. But in vast amounts, we see that water has a bluish tinge. This could account for some, but not all, of the blue of the sea. When we look out from the shore, the glassy face of the water acts as a mirror, It reflects blue on a clear day or grey from the clouds. Seen from above, the deep ocean looks blue because blue rays of light are reflected upwards from deep below, much as the blue rays of light are scattered over the sky.
The gases of the air and the liquid water of the sea, however, play different tricks with the rainbow colors hidden in white light. The particles of the air bounce back the short waves of the blue rays for us to see. The long waves of red, orange and yellow are absorbed by the surface layers of the sea and the blue rays bounce back from perhaps a mile below.