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So, if you have a basic, elementary understanding of how light works, you can say that black means all the light photons are absorbed, but darkness means that there aren't any photons to absorb. How can you absorb something, if there isn't anything to absorb?

Another solution people have been giving me is that black is also the absence of light. This just brings us back where we started, since darkness is the absence of light. Why is the absence of light black? This question has me stumped. Why is this the way it is?

Thanks in advance!

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    $\begingroup$ Why is the absence of light black? Isn't this more just a question about perception rather than physics? $\endgroup$ – BioPhysicist Apr 1 at 17:59
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    $\begingroup$ Surely this is just how our brains perceive the lack of visible light? $\endgroup$ – Alex Gibson Apr 1 at 17:59
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    $\begingroup$ I’m voting to close this question because it is about human visual perception, not physics. $\endgroup$ – G. Smith Apr 1 at 18:12
  • $\begingroup$ Should I have posted it somewhere else, @G.Smith? $\endgroup$ – Questioner Apr 19 at 14:36
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    $\begingroup$ @Questioner Yes, but I can’t recommend a particular SE site because I don’t know their policies. $\endgroup$ – G. Smith Apr 19 at 16:29
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you can say that black means all the light photons are absorbed, but darkness means that there aren't any photons to absorb. How can you absorb something, if there isn't anything to absorb?

Your perception of "Black" is not due to what is absorbed, but to what is emitted.

Why is the absence of light black?

Your human visual system registers the receiving of no photons as black. It does not care why there are no photons.

The absence of illumination for a surface produces the same result (from a human point of view) as the surface absorbing all (visible) light.

I do not think you can say black is a color, BTW. You can describe a color is a variety of ways and typically you get shades of a color all the way down to black. Black could be any color (hue), it just a description for a zero level of luminosity.

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    $\begingroup$ @thephysicist Reputation points are always welcome, however we generally recommend you wait a good 24 hours or more before accepting an answer as a better one may turn up if you give it time and it is a globally accessed website. $\endgroup$ – StephenG Apr 1 at 18:47
  • $\begingroup$ Your last paragraph is wrong by several reasonable definitions. What you've described there is the property of being "achromatic", but that's not the same as not being a color. (Despite the roots of the word unfortunately making it further seem like it's not a color, there is wide usage of the phrase "achromatic color".) But, as in my answer, the word "color" has several related but different meanings depending on who is using it and in what context. $\endgroup$ – Brick Apr 1 at 19:29
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The color "black" is what your mind perceives when no light reaches the cones and rods in your retina or some part of your retina.

There can be more than one reason that no light reaches your retina. One is that there are no sources of light in your vicinity ("darkness"). Another is that there are sources around but an object in your field of view absorbs all of the light incident on it (the object is "black").

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  • $\begingroup$ But why do our eyes perceive it as the color black? $\endgroup$ – Questioner Apr 1 at 18:07
  • $\begingroup$ Your eyes don't know why no photons arrived. They just know that they didn't. Black isn't so much a color (physically or psychologically) as it is the mind's interpretation of having no colors present. $\endgroup$ – Brick Apr 1 at 18:11
  • $\begingroup$ So, black isn't really a color? $\endgroup$ – Questioner Apr 1 at 18:12
  • $\begingroup$ I suppose it depends on how you're using it. If you ask for a black crayon, then you're giving it common-language usage as a color. From a physics perspective, it just means no light energy in the wavelengths of your detector. (In this case the detector is the eye itself.) Psychologically it is the response of the mind to not receiving signals from the retina indicating that light arrived. (That's usually because no light arrived, but it could result, for example, from damage to the eye or the optic nerve.) $\endgroup$ – Brick Apr 1 at 18:15
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    $\begingroup$ It's pretty much a definition at the level you're asking it now. Your eyes and brain (physically and chemically) and your mind (psychologically) have a specific reaction to this to the condition of no light at the eyes. We call that "black". (Why is 700 nm light "red"? Well, essentially the same reason. Your eyes, brain, and mind have a repeatable reaction to it and we gave that a label of seeing the color "red".) $\endgroup$ – Brick Apr 1 at 19:20

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