See Why the Sky Is Blue and Sunset Is Red - Easy Experiment

The sky is blue on a sunny day, yet red or orange at sunrise and sunset. The different colors are caused by scattering of light in the Earth's atmosphere. Here is a simple experiment you can do to see how this works:

Blue Sky - Red Sunset Materials

• water
• milk
• transparent container with flat parallel sides
• flashlight

A small rectangular aquarium works well for this experiment. Try a 2-1/2-gallon or 5-gallon tank.

Any other square or rectangular clear glass or plastic container will work.

Conduct the Experiment

1. Fill the container about 3/4 full of water. Turn on the flashlight and hold it flat against the side of the container. You probably won't be able to see the beam of the flashlight, although you may see bright sparkles where the light strikes dust, air bubbles, or other small particles in the water. This is much like how sunlight travels through space.
2. Add about 1/4 cup of milk (for a 2-1/2 gallon container -- increase the amount of milk for a larger container). Stir the milk into the container to mix it with water. Now, if you shine the flashlight against the side of the tank, you can see the beam of light in the water. Particles from the milk are scattering light. Examine the container from all sides. Notice if you look at the container from the side, the flashlight beam looks slightly blue, while the end of the flashlight appears slightly yellow.