Create a sunset effect in a container! Find out what types of particles in our atmosphere create a colorful sun. This experiment demonstrates how smog, smoke, chemicals, and dust in the air effect sunlight. You can tie this project into other topics like global warming, weather patterns, visible light wavelengths, and atmospheric science.
Difficulty Level: Easy
Project Time: 15 minutes
STEAM Concepts: Science, Technology, Math
Question: Do colorful sunsets happen because of the color or size of particles floating in our air?
¼ teaspoon measuring spoon
a small, rectangular, glass or plastic container with flat, parallel sides that holds around 32 fluid ounces
a small flashlight with a narrow beam (keychain flashlights or cell phone flashlights work well)
Sometimes, during a sunset or when there are wilfires that fill our air with smoke, the sun looks yellow, orange or red. Small things floating in our air like dust, smoke, or smog, can break up sunlight and make different colors appear. The water in this experiment will represent our air, and the flashlight will act like our sun. Which substance – cinnamon, turmeric, or milk, will make the most colorful sunset effect? Does the size of the particles or the color of the particles effect the color of light?
1. Fill the plastic container with water. The water in this project represents our air – the clean water is like a day with clear air.
2. Turn the flashlight on and hold it against the side of the container so that the light is shining through the longest length of the container. From the other side, look through the water at the flashlight beam. What color is the light?
3. Mix ¼ of a teaspoon of milk into the water – this is like adding dust, smoke, or other tiny particles to our "air". What color is the light from the flashlight now?
4. Rinse the container out, fill it with clean water, then mix the cinnamon into the water. The particles if cinnamon are much larger than the tiny particles of milk. Shine the flashlight through the water the same way again. What color is the light? Rinse and repeat the test with the turmeric.
5. Did the color of the stuff you mixed into the water change the color of the light? Keep experimenting! What other things can you mix into the water?
Fill the container with water and 1/4 teaspoon of milk again. This time, try looking at the light by shining it through the short length of the container, then the long length. Does it change the appearance of the light? When the sun is rising or setting, it's rays are traveling through more of our atmosphere compared to midday - just like the flashlight when you shine it through the long length of the container. The sunlight streaming through our atmosphere at sunrise and sunset has a greater chance of being scattered by tiny particles in our air because it is passing through more of our atmosphere.
Tiny pieces of stuff floating in the air like pollen, dust, smoke, ash, or chemicals are called particulate matter. Small particles scatter sunlight more than larger particles. When our air has tiny particles in it, the sunlight doesn't just separate – some of it gets reflected back into space. This means less energy (and less heat) gets through to the ground. Some scientists are researching how using particulate matter might help fight global warming. They call this field of research geoengineering.
Article on how air pollution effects sunlight: https://phys.org/news/2019-08-air-pollution-sunlight-earth-surface.html
Sun-diming experiment for battling global warming: https://www.nature.com/articles/d41586-018-07533-4
Nasa's site about the composition of earth's atmosphere: https://terra.nasa.gov/science/atmospheric-composition
NOAA site on atmospheric layers https://www.nesdis.noaa.gov/content/peeling-back-layers-atmosphere
Author - Brandy Stone