The Sky

When the sun shines brightly and a few clouds scatter the sky, the sky is blue. We see the sky everyday, and yet the sky is always blue. Except during cloud coverage and sunsets, the sky never eludes its blue color. Because I see the blue sky everyday, I have always wondered why the sky is blue and not green or purple.

Here is a science made simple link about why the sky is blue

The sky is blue because of the light that enters our eyes.
Before we answer the question, "Why is the sky blue?" we must first know what light is.
The reason we all are able to see with our eyes is that light enters our eyes. Light exhibits the characteristics of a wave. Light's waves may be visualized as a curvey line.

Waves display a pattern of alternating crests (the top curve of a wave) and troughs (the bottom curve of a wave). The distance from one crest to another is the wavelength.





A wave, wavelength (distance between crests), frequency





A wave, crest (the top), and trough (the bottom)

All waves have a frequency. The frequency of a wave is the number of waves that are made per second.



Take a look at this link to see an animation of wave frequency



As the frequency of a wave increases, the wave length decreases. As the frequency of a wave decreases, the wave length increases. The frequency of a wave of light determines the light's color. When sunlight is separated, the light is separated into many different colors. Sunlight may be separated through a crystal prism, glass, or rain drops. Rainbows are created by the seperation of the sun's light through rain drops.

sunlight may be separated into colors by raindrops...rainbows!

The earth's atmosphere also has a role in separating the sun's light. The atmosphere is composed of oxygen and nitrogen gasses. Blue light has a high frequency and a short wave length. The wave length of blue light is about the size of an oxygen atom. Because of the wave length the size of an oxygen atom, blue light interacts with the oxygen in the atmosphere. The light is scattered by this reaction. Because the scattered blue light enters our eyes from many different angles, we all see the entire sky in the color blue.