Alright, I’m taking the bait.

The topic for this article was suggested to me by my boss who engaged me in a conversation regarding the existence of black. The suggestion that I write on such a topic followed a statement made by me that my Not A Blog™ was about, quote—various things—endquote. Since philosophical musings on the nature of reality is one of those various things, I’ll discuss the idea here.

Firstly, one must establish an agreed upon definition of black before any discussion can take place. I defined black this way, and nobody had any objections; I think it stands. “Black” is the term we use to describe an area that has little to no photons of a wavelength of the visible portion of the electromagnetic spectrum emanating from it.

Discussion Point One: Black refers to different things whether it’s pigment or light. Black arises from light when there’s none present, whereas black arises from pigments when you mix all the colors. A pigment is seen as having a particular hue because it’s absorbing all the wavelengths of light except the one that is that you see as that color. The number of photons determine the value: the less photons, the darker and closer to black the pigment appears. If you mix two opposite pigments together (complimentary colors), you get gray, because now you’re absorbing all wavelengths in equal amounts. You’re also reflecting a certain amount of all wavelengths in equal amounts, which is why you see gray and not black. (In practice, you usually get a muddy, crappy looking brown because it’s difficult to mix precisely the right amounts of pigments to cancel out all the color, and because pigments aren’t always exactly complimentary. I have done it a few times in the past, though, and it’s actually pretty cool to see.)

With light, on the other hand, what you’re seeing is not the reflection of colors due to the pigment of the object—at least not exclusively. If you have a white object appearing in blue light, for example, it looks blue due to the fact that the light source is only emitting color of that wavelength. This could be due to a couple of factors: the type of light source, a gel or colored bulb which only allows a certain range of frequencies to pass, etc. But in that case, the emitted light is only of a certain part of the spectrum to begin with. If you’ve ever seen a blue car underneath a sodium-arc lamp at night, you’ll notice that it looks black, or very close to black, because the wavelengths of light being emitted by the lamp are complimentary to the wavelengths that are being reflected by the car. When you have this absence of photons being reflected into the eye, you have black.

Discussion Point Two: What if you have no light? If you have no light, you have black because no photons are being emitted from the area you’re looking at. If you have a light but nothing to reflect it off of, you still have black for the same reason.

Discussion Point Three: What happens when you take away the pigment? If you have no pigment, you have the color of the ground—the canvas or background. This can be white, but it can be black, too. In that case, as you add pigment, that area of the canvas now absorbs one (or two or three) less wavelengths than the black background surrounding it, and so does not appear black.

There’s no such thing as pigment without it being attached to something. Yes, you could have a blob of the stuff floating around, but in that case, the pigment is simply its own object, and acts as the thing from which light is radiating. If you have a blob of matte black pigment in space and it’s not reflecting anything, you still have black because, again, no photons are emanating from anything—not because the pigment, in and of itself, is “black”.

Discussion Point Four: Assuming one is blind from birth, does this blind person see black? No, in the same way a person who has deuteranopia color blindness does not see green and therefore does not have the concept of “green” the way non-color-blind people do. It might be accurate to say a blind person sees emptiness or nothingness, however, we don’t have a concept of this because we’ve never experienced seeing nothing. Or rather, we might have, but we call that black because it would be an environ from which no light emanates, and that is the situation for which we use the word.

Robert Heinlein plays with this idea in his short story, —And He Built A Crooked House. In the story, an architect builds a house in the shape of an unfolded hypercube. The house is in California, which is important because an earthquake hits the area and the architect and his client find, much to their bemusement, that it collapsed into four spatial dimensions, leaving a building one room in size from the outside, but having eight interconnected rooms through the fourth dimension on the inside. Traveling to the outer boundary (the eighth room, as it were, since the other seven would be locally connected), the architect opens a window that faces out.

Teal [the architect] lifted the blind a few inches. He saw nothing, and raised it a little more—still nothing. Slowly he raised it until the window was fully exposed. They gazed out at—nothing.

Nothing, nothing at all. What color is nothing? Don’t be silly! What shape is it? Shape is an attribute of something. It has neither depth nor form. It has not even blackness. It was nothing.

The joke is, of course, that we can’t imagine nothing without imagining blackness because that’s what we’ve come to associate with no photonic information. It’s nothing/black.

Discussion Point Five: Do technological devices that can see more of the electromagnetic spectrum contribute to what humans can experience? Conditionally, yes. However, it doesn’t change the original definition of black. Cameras exist which can see infrared and ultraviolet, and shift this information into the visible portion of the spectrum that we can see, but this doesn’t change the definition of black that is the absence of photons in the visible part of the electromagnetic spectrum. The caveat being, of course, that “visible” means “visible to the unaided human eye”. This varies; people with better eyesight will see more of the spectrum than others. But we all have a point of reference to describe the concept.

The question of whether or not black exists at this point becomes almost pedantic. The answer is: yes. The confusion arises, I believe, because black is defined in terms of what is not rather than what is. That can be dangerous territory, not in the least because so few people understand the limitations (and strengths) of arguing from absence. The general rule of thumb is, “you can’t prove a negative”—a little logician inside joke since the statement itself is a negative making a definite statement. If you can’t prove a negative, you can’t prove you can’t prove a negative, meaning there could be instances where you could prove a negative, though they remain undefined. Gödel’s Incompleteness writ bare. Better to say, “you must prove positives.” The resulting challenge to “prove it” can be answered with a treatise on the basis of formal logic stemming independently from the linguistic concepts used to describe said logic—and hope your audience just leaves due to your exceeding erudition.

(As I tried to do in the preceding paragraph.)

But I digressed from the main point that there is black. It exists as a concept or a descriptor of a certain state of events rather than a physical thing—in fact, describing the lack of a physical thing (photons). It’s really a matter of perception. Some people are going to see less photons, and so their version of “black” might be different from someone else’s version of “black”. Besides all that, there’s no way to know what colors anyone else sees. Everyone calls the sky “blue”, but how do you know that someone else’s blue isn’t what you call red? You know the sky is blue because that’s what everyone else calls that particular color, but you can’t ever be sure that you’re not the odd man out. Regardless, as long as one can see photons, however few in number, they will then be able to make a comparison to the state of seeing no photons: a state we call black.

A more interesting philosophical question in light, so to speak, of Heinlein’s short story might be: is there such a thing as nothingness? Isn’t nothing something?

However, having answered the original question that was posed to me, I think the issue of nothingness is an essay for another day.

-Ted