Science Experiments for Kids : Sunset in a jar science

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A fun science experiment for kids using just water, milk and a flash light. Recreate the sky and understand optics in a hands on way.

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Materials

Glass Jar or tall cup
Milk
Flash Light
A dark room

This popular and fun science experiment was on our to-do list for a long time! We adjusted the original experiment a little bit and focussed more the effect of milk {dust particles in the atmosphere} in the water. Start by setting out clear water in a tall glass jar/cup. Have some milk { I used 2%} near by and a measuring cup/spoon near by.

First shine the flash light through the clear water in the jar.

Explanation : The flashlight is acting like the Sun and the clear water is acting like the atmosphere. The water is like the atmosphere without ANY dust particles suspended which is never the case. The light doesn’t get scattered.

Now to 1 cup of water add about 2 TBSP of milk. Move the science experiment to a dark room to have the best experience. Shine the flash light through the side of the jar and observe the color. You should start seeing the liquid in a pale blue shade. By adding the milk you are adding more particles to the water { suspended dust particles in the atmosphere – the fat molecules in the milk are going to make the light react differently} Move the flash light and shine it from different positions { behind the cup and observe from the top} The different positions of the flash light correspond to the different positions of the SUN { rather the different positions of the earth relative to the Sun}

Why do you see the blue? How does it relate to the blue sky?

Out of the colors of the visible spectrum blue scatters the most. At midday { when the flash light is to the side} the sunlight doesn’t have to travel much to reach Earth { compared to sunrise and sunset times}. Human eye captures the blue light which scatters the most during the day.

Increase the amount go milk and continue the experiment. You will see the color change and you will observe more of a yellow or occasionally an orange depending on the type of milk you are using. Change the positions of the light source which corresponds to different times during the day. The added fat molecules in the liquid gives more intensity and now you are able to view the yellow in the light.

Move the light source and place it behind the glass and view. When you are moving the light source you are recreating the position of the Earth during sun rise and sunset.

Now for the sunset!!

Try filing up a jar completely with milk. So this is like the atmosphere filled with maximum amount of dust particles. You will see a gorgeous deep yellow/orange in the jar. During sunrise and sunset, owing to the Earth’s position relative to the Sun the sunlight has to travel a little longer to reach Earth. This gives the red and orange shades { which don’t scatter as much as blue} a chance to be visible to the human eye.

Explanation : So you DON’T want a bright red/orange sunset. Why?

The more polluted the atmosphere is the brighter, redder the sunsets are. The large number of dust particles contribute to the scattering.

Try this science experiment with different flashlights, differing amount of milk, different types of milk, shapes of the container. Vary the shape of the container. A good twist would be to use one of these Aqua Balls containers to hold the milky water. The spherical shape of the water bottle will mimic the shape of the Earth. Be sure to use the clear bottle after removing the wrapping.