Weather Station

Why is the Sky Blue?

White light really is a combination of all colors. When sunlight shines through the weather zone, water droplets and other moisture refracts, or bends, the light. The refraction of pure sunlight causes the sky to appear blue.

Scientists call this "weather zone" the troposphere. This important part of the atmosphere is made of mostly nitrogen and oxygen. About three-fourths of the troposphere is nitrogen. Less than one-fourth is oxygen, or just about 21 percent. The remaining one percent is made of a gas called argon, and tiny traces of other gases.

When sunlight shines through these gases, blue light is scattered in all directions. You see the blue light that happens to come in your direction. All colors of light are scattered by water droplets in the sky.

A deep blue sky means that there is very little moisture in the troposphere. A pale blue sky, or a gray sky, means there is lots of moisture in the weather zone. That is why gray skies are usually rainy skies.

 

 

 

 

 

 

 

 

 

 

 

 

Try scattering light yourself! Visit Patterns in Nature, another ASU Web site.
Go!

Sunlight contains all colors, but the sky looks blue.
Why?