Color me smart: 5 reasons why things are the color that they are

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Color me smart: 5 reasons why things are the color that they are

By Linda | February 12, 2008

1. Why is the sky blue?

A. A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colors because the blue light has been scattered out and away from the line of sight.

2. Why is snow white?

A. The answer lies in snow’s messy construction. A beam of white sunlight entering a snow bank is so quickly scattered by a zillion ice crystals and air pockets that most of it comes zinging right back out of the snow bank. No one wavelength is preferentially absorbed or reflected, so snow is essentially the color of the sunlight reflecting off of it — white.

3. Why is blood red?

A. Red blood cells are red because they contain a protein called hemoglobin which is bright red in color. In humans and other hemoglobin-using creatures, oxygenated blood is bright red. This is due to oxygenated iron in the hemoglobin. Deoxygenated blood is a darker shade of red. It is a misconception that human blood is ever blue in color.

4. Why are plants green?

A. Plants are green because they contain a substance called chlorophyll. Green plants use chlorophyll molecules like tiny antenna that actually harvest the Sun’s energy. The plant feeds itself by using this energy to produce sugars which it uses as fuel in a process known as photosynthesis. If we shine white light on chlorophyll, its molecules will absorb red and blue light. The other colors are reflected back to our eyes resulting in the green color that we associate with plants.

5. Why is pee (urine) yellow?

A. The yellow color in urine is due to a chemical called bilirubin. Bilirubin and other chemicals are produced when the body breaks down worn-out red blood cells. Most of these chemicals are partly broken down in the liver, stored in the gall bladder, broken down some more in the intestines, and excreted in the feces (this is what makes feces brown), but some remains in the bloodstream to be extracted by the kidneys where, converted to urobilins, give urine that familiar yellow tint.

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