Why Are Sunsets Red Science Experiment STEM (Video)

This science experiment aims to explore the reason behind the color of sunsets and to understand the physics of light and atmospheric conditions that lead to this phenomenon.

By using a simple setup, you can observe and analyze the scattering of light in the atmosphere, and how it is affected by the angle of the sun and the composition of the air.

From the last experiment, we know that when light (representing the sun) passes through a clear fluid (representing air) holding small particles (representing dusts), blue is scattered more than most other colors.

That’s why when we look at the sky during the day, we can see a blue tint.

As the light travels through a longer distance (the sun is farther away during sunsets), since the blue has been scattered, only the yellow/orange colors are left (More scientific explanations).

Besides moving a flashlight around, sunset colors can also be created when white light travels for a long distance through a medium filled with small particles, here are two ways you can create a homemade sunset.

orange sunset science experiment

Why Are Sunsets Red Orange Experiment

Active Time: 30 minutes
Total Time: 30 minutes

Let's make this homemade sunset.


  • water
  • white soap / milk powder
  • a flashlight that emits white light (I used TaoTronics LED light bulb)


  • a rectangular clear glass container or a long clear drinking glass
  • adult supervision


  1. Fill the glass with water.
  2. Dissolve a little bit of soap in the water to get a cloudy solution.
  3. In a dark room, point the flashlight at the cloudy solution from one end of the container.
  4. Observe the solution to see a hint of blue color near the light. The solution's color changes to yellow and then orange as you farther away from the light source.

    When white light lights up one side of a long container, the water inside turns orange
    When white light lights up a glass of water from the top, the bottom of the water turns orange

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