why the sky is blue

While I was home on Thanksgiving break I was spending some quality time with my family. My little cousin Mia is five years old and full of questions. While playing at the park with her, Mia asked me why the sky was blue and not pink like her favorite color. Not knowing the answer to the question myself, I quickly made something up and told her the sky was blue because water is blue and the rain comes from the sky. She thought it made perfect sense, but I knew there had to be a scientific reason. My little cousin's curiosity prompted me to do some research.


I found that the answer is physics. The light from the sun looks white, but is really made up of all the colors of the rainbow. Light travels in waves and each color has its own wave length. Blue light has the shortest and smallest waves. Light will always travel in a straight line unless something gets in its way to reflect, bend or scatter it. As the sun shines and its light travels to earth, the particles in the atmosphere cause the light to scatter. Blue light scatters more than any other color because it travels in shorter, smaller waves. As you look higher up, the sky looks dark blue. As you start to look lower the color blue gets lighter and lighter and closer to white.

blue light.jpg
If you exam the photo above it explains why the sky fades from dark blue to almost white. As sunlight travels through the air, the air molecules scatter and keep re-scattering the light waves in all different directions. All the scattering that is taking place combines all the colors of the different light waves and produces the almost white color that is seen closer to the horizon.

The position of the sun determines how its sunlight will travel through the air. As the sun begins to set, blue light waves are being scatter by even more particles in the atmosphere. With blue light waves being scattered, it allows more of the red and orange light waves to be seen by the eye. Thus, creating a beautiful, colorful sun set. Now, once my cousin gets a little bit older, I will be able to explain the scientific reason as to why the sky is blue.


Hey Jessica!

This question always pondered me too, so I'm glad you blogged about it! I knew the color of water was blue because it reflected the color of the sky but I didn't know the color of the sky was blue because it was the slowest traveling wave. It does make sense to me now though, sunlight represents all the colors, therefore it's white. So at night, the sky is black because there is no color, there is an absence of color, it all makes sense now. Your blog is also the answer to why people say the sun looks yellow. During sunrise and sunset the wavelength of light from the sun is less deviated, therefore it's yellow. Thanks!

More of it can be read about here

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