Colors are everywhere. A red ball bouncing around during a kickball game… a black and white dog taking a stroll at the end of a leash… green grass under your bare feet… and a brilliant blue sky on a clear, sunny day.
If you’ve ever wondered what makes the sky blue, today’s Wonder of the Day is just for you.
Have you ever wondered…
- Why is the sky blue?
- What color is sunlight?
- Why does the sky turn red and orange at dawn and dusk?
Did you know?
The sunlight we see each day, called “white light,” may appear colorless, but it is actually full of a lot of colors mixed together. This is why you see a rainbow when you shine white light through a prism.
The prism separates the white light into each of its colors: red, orange, yellow, green, blue, indigo and violet.
Each of the colors is made up of its own wavelengths, kind of like a unique fingerprint. Red has the longest wavelength, violet has the shortest and all the other colors are somewhere in the middle.
When you look at an object, such as a yellow sunflower or a red wagon, the color you see is actually the color of light the object reflects to your eye. A yellow sunflower reflects yellow wavelengths while absorbing all the other colors. A red wagon, on the other hand, reflects red wavelengths.
So how does the air in the sky have a color? The Earth’s atmosphere is filled with gas molecules. As white light from the sun passes through the atmosphere, colors with longer wavelengths, such as red, orange and yellow, pass through.
Blue and violet wavelengths, on the other hand, are absorbed by the gas molecules and scattered across the sky. Your eye sees these reflected wavelengths as blue.
Of course, you’ve probably seen the sky turn brilliant shades of orange and red during a sunrise or sunset. When the sun is low near the horizon as it rises or sets, the wavelengths have farther to go in order to reach your eyes.
This causes the shorter blue wavelengths you see during the day to scatter even more, clearing the way for longer wavelengths like red and orange to reach your eyes.
Try it out!
Would you believe you can make blue skies and brilliant sunsets in a jar at home? It’s true! You will need the following items:
- Clear glass jar or a drinking glass
- Water
- Milk powder
- Flashlight
- Dark room
Fill your clear glass or jar with water, add about 1/2 to 1 teaspoon of milk powder and stir slowly. Turn off the lights and shine the flashlight on the surface of the water.
Watch the water in the glass from the side near the flashlight. You may notice a bluish tinge.
Now, hold the flashlight to the side of the glass and look through the water directly at the light. It will now look red. If you put the flashlight under the glass, the light will appear redder than before.
Why does this work? The fat molecules from the milk powder in the water behave like air molecules. They scatter the light from the flashlight.
When the light shines in the top of the glass, blue light is scattered, and a bluish tinge can be seen out the sides. When you look through the water directly at the light, you peer through more of the milk fat molecules. This causes more scattering of the blue light and makes way for red wavelengths.
Wonder words to know and use:
- signature
- brilliant
- prism
- indigo
- wavelength
- atmosphere
- molecule
- horizon
- tinge
Still wondering?
Visit ReadWriteThink’s Explanation of a Weather Saying lesson to learn the explanation behind the old weather saying, “Red sky at night, sailor’s delight, red sky in the morning, sailor take warning.”
Wonder what’s next?
What’s in a name? You may be surprised. Tomorrow’s Wonder of the Day just might blow you away!
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Wow! This wonder was amazing, Wonderopolis! I never knew that the sky was blue because of the white light from the sun (that is actually full of many colors) and the blue wavelengths passing through the air cause the sky to turn blue! I always thought that the sky was blue because it was just blue! Now I know the real scientific reason! Also, it is so cool how a rainbow can be formed when you shine white light through a prism which separates the white light into seven sections! (red, orange, yellow, green, blue, indigo, and violet). This wonder was so cool! It really made me wonder!
Hello, Sarah! We’re super happy to hear that you now know the reason why the sky is blue! You sure learned a lot of facts about the sun, colors and wavelengths by exploring this Wonder of the Day®! That’s a LOT of WONDERing…way to go!
This is a wonder that I have been wondering about, too. I hit the jackpot! This is sooooo cool. I never knew it was because of white light!
Thank you for leaving us this awesome comment and for letting us know you “hit the jackpot” by exploring this Wonder of the Day®, Kaley! You’re a GREAT Wonder Friend!
I think I have read more than 5 wonders this day. It’s very cool and awesome! My curiosity is increasing! I want to spend a lot of time in wonderopolis. Lots of luck to wonderopolis!!!
Thanks so much for the good luck wishes, Amoolya! We have really enjoyed reading all your great comments and are super happy to hear that you think Wonderopolis is cool and awesome!
Thanks for explaining it, Wonderopolis! This was such a neat thing to write about, too!
It makes us super happy to read comments like yours, 13! We really like when our Wonder Friends let us know they understand a little bit more about something they have WONDERed by exploring a Wonder of the Day®!
I always wondered about this! Thanks for the explanation! I love this website, too! My teacher showed me it today on her website.
We think it’s 100% AWESOME that this Wonder features something you’ve always WONDERed about, Taylor! We love hearing when that happens! Please tell your teacher we think she ROCKS for sharing Wonderopolis with you and your classmates!
I never knew that sunlight is also called white light. I didn’t know that at sun rise and sun set the waves had to go farther to reach your eyes. I didn’t know that each color was made of different wavelengths. I never knew that red had the longest wavelength and purple had the shortest. Do you know what types of gas molecules are in the air to filter the waves?
- Team Unger 14
Hello, Team Unger 14! Thanks so much for visiting this Wonder! We’re glad you enjoyed learning about light!