Polar bears and peacock feathers

For years I have been puzzled when people say that polar bears are not really white; they only look white. They also say that the dots on peacock feathers are not really blue; they only look blue. If polar bears are not white, what color are they really? They look white to me. If those dots on peacock feathers are not blue, what color are they really? They look blue to me.

Philosophical questions about colors and other qualities go back at least as far as Plato and Aristotle. These and other philosophers have tried to examine what an object is other than its qualities and what a quality is apart from the objects that have it. Can you define whiteness apart from indicating something that looks white, whether it is a field covered in snow or a polar bear? Can blueness exist apart from a quality of things that look blue? If something changes in color, how much has it changed? Has it merely exchanged one quality for another, or is it now a different object?

I know that the people who say that a polar bear looks white but is not really white were not engaged in that kind of philosophic discussion.

Among his many accomplishments, Isaac Newton revolutionized science’s understanding of light and vision. By demonstrating that a glass prism or a lot of raindrops could break a beam of white light into a rainbow, Newton showed that color and light are closely related. As understanding of light and vision grew from that observation, scientists realize that objects absorb some wavelengths of light while reflecting other wavelengths. We see the colors that are reflected without the colors that are absorbed. White objects are reflecting all the wavelengths of visible light; black objects are absorbing all the wavelengths of visible light.

But that still doesn’t explain how a polar bear could look white without being white.

I recently read an article about light and vision that finally explained what that means. Many of the colors we see in objects are caused by pigments, which are chemicals on the surface of that object which absorb some light waves and reflect us. Chlorophyll is a pigment in many plants that absorbs some wavelengths of light (using that energy to feed the plant) while reflecting green light. Anyone who has worked with paints understands how to blend different colors of paint to achieve the desired color. The mixture of paints absorbs some wavelengths of light while reflecting those wavelengths that the painter wants observers to see.

Polar bear fur does not contain any white pigment. It is the shape of that fur, especially when it is wet, that reflects white light. Peacock feathers do not contain any blue pigment. The shape of the surface of the feather reflects blue light while absorbing other wavelengths of light, causing the dots on the feathers to look blue.

If only people would have said it that way. Polar bears look white and are white even though their fur contains no white pigment. The dots on peacock feathers look blue and are blue even though their feathers contain no blue pigment. Yes, it requires a few more words to communicate the idea, but the communication is much easier to understand.

Interesting sidelight number one: A young man I know well likes to say that purple is not really a color. In one sense he is right. There is no purple wavelength of light. Look closely at a rainbow and you will see that the inner portion of the color is a deep royal blue, not purple at all. On the other hand, he is wrong. Blend a paint that reflects red light waves with a paint that reflects blue light waves, and you will have purple paint. Whatever you cover with that paint will be purple…or at least the color purple will be one of its qualities.

Interesting sidelight number two: Earlier this year a woman took a picture with her phone of a dress that was blue and black. She sent the picture to her daughter, who looked at the picture and thought that the dress was white and gold. You could blame the camera, but here it gets interesting. When the photograph went viral on the internet, people could look at the same photograph on the same screen under the same conditions, and some people saw a white and gold dress while others saw a blue and black dress. A few people could even alternate the colors they saw in the dress. For centuries, people have wondered whether we all see things the same way. When you and I look at something that we agree is red, are we seeing it the same way? The answer, we now know, is no. The dress photograph of 2015 has had its brief internet fame, but I predict that the photograph will appear in psychology textbooks and philosophy textbooks for years to come.

J.

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