Image source: Pexels.com

My son (6 years) is asking me a lot of questions which is great! The question he asked me yesterday was "Why is the sky blue during the day, red in the late afternoon and dark at night?"

I explained him what I remembered from school, that it has to do with the light waves coming from the sun and how these waves change length when they hit the gas molecules within earth's atmosphere.

He looked at me with big eyes, than turned around and started playing with his cars. Apparently he didn't seem to be really satisfied with my answer and so was I.

In an attempt to explain it to him in a better way, I researched the web to understand the process more detailed and like to share my findings in this post in case there are a few parents reading who like to be prepared for the same or similar question.

So lets break the whole subject down into small pieces so a child can understand it.

• What is light?
  Light is electromagnetic radiation (let's call it "waves") given of the sun. There are long waves and short waves, the human eye however can only see a certain range of these waves (let's call it "sunlight") coming from the sun.
  
  
• What is (light) color?
  
  Image source: Wikipedia.com

So we learned about the long waves and short waves within the spectrum that is visible to the human eye. To simplify, light with a short wave length look blue, light with a medium wave length looks green and light with a long wave length looks red.

• What is the atmosphere?
  The atmosphere is a layer of various gases but mainly nitrogen, oygen and argon (let's call it "air") that sourounds the earth and is hold in place by earth's gravity. Gravity? what!? Gravity is another word for pulling stuff to the center

Putting it all together

When the sun is shining high in the sky during the day, the sunlight that initially travels through space in a single wave get's scattered in all directions when hitting the air in the atmosphere.

Because the shorter waves (blue) of the sunlight are scattered more than the other waves, the sky looks blue to us during the day.

When the sun is shining low in the sky during the afternoon, the sunlight has travel a bit further to reach earth and also has to pass through more air in the atmosphere. Now the longer waves are scattered more around which means the sky looks red.