Experiment: The sky in a glass

Globule wonders...
Why is the sky blue?

Experiment: The sky in a glass


Hypotheses:
Have children tell you why they think the sky is blue. You may even push them to think further and ask them why they think the sky turns red when the sun sets.

Material:
A glass or other transparent container with straight sides
1 to 2 cups of water
½ teaspoon to 1 teaspoon of milk
A flashlight
Manipulations:

Pour water into the glass until is ¾ full.

Add the milk and stir well.

You will need your imagination for this experiment. Imagine that the water in the glass represents the air which surrounds you and that the milk represents tiny dust particles found in the air. These particles are so small you cannot see them...but they exist! The flashlight will play the role of the sun.

Go to a dark room with your daycare worker and friends. Bring the glass.

Once you are in the dark, your daycare worker will place the flashlight over the glass, directing the light onto the water's surface. Watch from the side of the glass (see diagram, first observation). What colour do you see? Look closely it is a very light colour!

For the second observation, your daycare worker will place the flashlight in front of you. This will demonstrate the position of the sun when it sets. What colour do you see?

The sun continues its descent for the third observation. You should see the same colour as in the second observation, only darker.
Explanations:
The white light produced by the flashlight is really a combination of all the colours of light. When the white light hits the small particles of milk suspended in the water, the blue colour separates itself from the others to the side. That is why you see blue when you observe from the side.

The same principle exists in air only the light from the sun hits dust particles. This is why the sky seems blue when the sun is over your head. When the sun descends to your eye level, the sky seems red. You can longer see the blue which is off to the side since the beam of light is directly in front of you.

Source: http://www.educatall.com/page/63/The-sky-in-a-glass.html