What do you mean gray doesn’t exist?

The world is not just black and white; there is a variety of shades of gray in-between. Or so they say. Cinematographers have used this theme for years, filming in black and white or muted colors, showing the bright colors only when something hopeful is worth seeing. But the phrase and all its implications has got me thinking. Is the color gray a color at all?

Well, the answer is no. Neither is black or white for that matter. For something to be classified a color, it needs to have a wavelength associated with it. In layman’s terms, if light passes through a prism, the color you put in is the color you get out.

Dispersion of White Light

Dispersion of White Light

It’s one of the first things that as a child that we all learn about sunlight: hold up a prism to it and you get a rainbow. Water droplets in the air form a rainbow across the cloudy sky. Light passing through a clear cup filled with water spreads a rainbow across the table. Children are fascinated by this. (So are cats for that matter, but for different reasons.)

The reason for this is because the light emanating from the sun contains a spectrum of colors, all different wavelengths. As the light passes from the air and through a medium of differing refractive index, such as water or glass, the light from different wavelengths is refracted by varying amounts. Among geeky physicists, of which I’m one, this phenomenon is known as dispersion.

Within astronomy, this dispersion of light as it passes through a prism is basis behind the instrument designs used for spectroscopy, an area of science that analyzes the wavelengths of light emitted from a given object. It is how astronomers can say with certainty that celestial objects have certain colors, and from years of experience, and countless hours of staring a computer models, it’s how they know what elements are present in our sun and the other stars surrounding us.

Spectroscopy uses the dispersion of light to help identify what elements are present. (Image source: http://chenresearchgroup.weebly.com/spectroscopy.html)

Spectroscopy uses the dispersion of light to help identify what elements are present. (Image source: http://chenresearchgroup.weebly.com/spectroscopy.html)

But what about white, black and gray?

White is the summation of all wavelengths within the visual spectrum. All wavelengths are either emitted by the object, or reflected, if it’s not a light source. Black, on the other hand, is the absence of all wavelengths within the visual spectrum; all light is absorbed. It’s why a black hole is called a black hole, because all light is absorbed by the beast. White and black don’t have just one wavelength associated with them. The same can be said about gray.

We see an object as gray when it absorbs most of the light present, but reflects all wavelengths, but in equal amounts. Let me just take a step back here.

We see a red apple as red because when light hits that apple, the surface of the apple absorbs all wavelengths of light, except the wavelengths we associate with red. Those wavelengths are reflected. Something yellow will reflect light in the yellow portion of the spectrum; same with blue and any other color. But remember I said that white is the summation of all colors. Hence, something white will reflect all light. Something gray partially reflects and partially absorbs.

Paw Writer... Move out of the way so I can see.

Paw Writer… Move out of the way so I can see.

Now to complicate matters, on a computer screen, gray doesn’t exist at all. Gray is actually a series of black dots on a white background. The higher the density of black dots, the darker that shade of gray.

And gray paint… Well, that’s an entirely different beast. Artists and scientist can’t even agree about the pallet for primary colors. Hmm… Maybe I’ll go into that one next time.

But for now, gray will be just a color in language. In reality… Well, the world is just filled with so many colors that I would take a lifetime to name them all.


P.S. Come and follow my colorful world on Twitter or Facebook.

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