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Meteorology Science Fair Project

Why is the Sky Blue?

Why is the Sky Blue? | Science Fair Projects | STEM Projects
Have you ever looked up at the sky and wondered why it's blue? Well, it's all about the way light interacts with the air. When sunlight passes through the atmosphere, most of the longer wavelengths pass straight through. But the shorter wavelength light is absorbed by the gas molecules and scattered all around the sky. This is why the sky looks blue!


The hypothesis is that the sky is blue due to Rayleigh scattering.

Method & Materials

You will fill a glass or jar with water and milk, take it into a darkened room, and observe the water in the glass from the side, the side of the glass, and the top of the glass.
You will need a clear, straight-sided drinking glass or clear plastic or glass jar, water, milk, measuring spoons, and a flashlight.


The experiment showed that when light passes through the air, some of the blue light is scattered all around the sky. This is why the sky looks blue. The experiment also showed that when the light shines in the top of the glass, the water looks blue because you see blue light scattered to the side. When you look through the water directly at the light, it appears red because some of the blue was removed by scattering.

Why do this project?

This science project is interesting and unique because it allows students to observe the same phenomenon that causes the sky to be blue in a controlled environment.

Also Consider

Experiment variations to consider include using different liquids in the jar, such as oil or juice, or using different colors of light, such as red or green.

Full project details

You can find additional information and details for this science fair project here. Have fun exploring!

Related video

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