From what I understand, humans can see red green and blue and everything in the middle. Some animals I’ve heard see more colors than us, so what’s to say that some things in nature are colors that we don’t see? Who’s to say that some apples are red? And instead a different color that we don’t have a name for because we can’t process it?
How can we tell if this “apple” is as a matter of fact “red”.
In: 75
Colours are arbitrary labels put on light waves of different size.
That’s why we talk about the spectrum of light.
The biggest waves that we can see are red; the bigger waves that aren’t visible immediately after that are what we colloquially call infrared.
On the other end the “smallest colour” we see is blue, with the light waves smaller than that disappearing off the visible spectrum into ultraviolet.
It’s not like there’s a secret colour like “blurple” at the end. It’s just certain animals have eyes with cones than can process a shifted or wider spectrum of light.
A red apple is red to everyone because we can observe the light being reflected from it and provide a non subjective measurement of it.
There are two ways of looking at this question.
Aesthetically, an apple is red because that is the color we can see. That’s it. Color is a human-made concept, so it’s rather natural for us to limit the concept of color to what we can see. We can see the color red, so red is a color. We can’t see radio waves, so radio waves aren’t a color.
Scientifically, we can measure all the possible wavelengths of light that reflect off a surface, even those we can’t see. This way, we can categorize an object by what light it reflects and call that its color.
When you shine light on an object, it reflects that light. However, it might not reflect *all* of the light, because some of it may be absorbed by the object. Using advanced equipment, we can tell exactly what wavelengths of light it absorbs and what wavelengths it reflects.
Color is defined by our own sensory apparatus, which can detect only a limited set of wavelengths of light, known as the visible spectrum. Two objects that reflect primarily red light in the visible spectrum but wildly different wavelengths outside the visible spectrum will both appear to us as red. If we could sense those other wavelengths, the objects would presumably look different in some way.
We could, if we wanted to, define an object’s color in terms of the entire spectrum of light, not just the visible portion, but this would be silly for two reasons. First, we don’t have any intuitive sense of what light “looks like” outside the visible spectrum. We know that other animals can see different colors, but we don’t know what that experience is like. Second, it would be impractical for most situations where color is used. If someone told you to bring them the “super-red fruit,” how would you know whether they meant an apple or a strawberry?
We can tell the apple is red because we defined “red” as the “color of an apple.” We gave words to all the colors before we knew anything about different wavelengths of light or the color receptors in the retina.
People with certain types of color blindness and animals with different eye structures don’t perceive red the same way you or I do: To a dog, the apple looks to be a shade of brown, even though it is reflecting the same wavelengths of light. Likewise, certain species of birds and insects would see that a flower we would say is just red, and see that it is actually highlighted with ultraviolet stripes. But to us both the apple and the flower are red, because “red” is the word we gave to the subjective experience of seeing those things.
“Red” is a social construct. It’s the term that English speakers use to identify electromagnetic wavelengths within a certain range (620-720 nanometers). We know that an apple is “red” both from our vision, and also because we can construct devices that react when struck with a photon whose wavelength falls within a given range.
We do have names for colors we can’t see. It’s just that, since they are not colors that we interact with on a casual level, the names tend to be rather technical. There are names for the different categories of non-visible light: Radio, microwave, infrared, ultraviolet, X-ray and gamma ray. But specific “colors” are simply identified by their wavelength.
The colors that we micro-divide into millions of different shades are simply the ones that most people interact with on a daily, casual level, and they represent a teeny tiny slice of the different wavelengths of light. They are the most common wavelengths that we see on Earth, and since we interact with them directly and without the need for specialized equipment, we have given them specific names so that we can talk about them casually.
It can be misleading to think of light as only the visible light our sun gives the planet. The truth is visible light is only a very small sliver of a large spectrum of energy. On the low end we have things like radio waves. On the high end we have things like x rays. All of them are the same energy at higher and higher frequencies. In between we have visible light. That is the energy frequency the human has evolved the cells to capture the reflected energy and interpret it as color. Other animals have evolved to see smaller bands of energy. Even still other animals have evolved to see wider bands. So where we can’t see infrared or ultraviolet light some animals can pick up those energies which are invisible to us and interpret them to colors which we have no name for.
So color is an incredibly subjective experience. We can describe it mathematically by measuring the different energies it reflects. But colors themselves are the human way we describe an experience and just like any other sensation our descriptions may differ. For instance what I describe as pink, others might call rose or their native language might describe it in a way that translates to “very light red”
Though on the note of “pink”; did you know it’s not a color that exists on the color spectrum. Pink is simply the way the human brain interprets white light that has most or all of the green wavelength removed. Another animal may see it as a different “color”. Again just an example of how the way we describe our experience of color is very subjective.
>so what’s to say that some things in nature are colors that we don’t see?
Uh, almost everything radiates or reflects wavelengths we can’t see. They can ALSO reflect wavelengths we DO see at the same time.
Bird wings are a good example. They have coloration and patterns in the UV space that other birds can see, but we can’t. That doesn’t stop us from seeing the bird have blue wings.
>Who’s to say that some apples are red?
The measurable spectography of apples, and the definition of “red” as radiation with a wavelength of ~650nm.
This isn’t some mystic shit, we can measure it.
Apples are red because they “reflect” that part of the spectrum that we can see, and object could reflect red and also part of the ultraviolet for example but since we can only perceive red we still say that object is red. We can use a thermal camera to “see” infrared but we don’t say it’s a different color because we can’t perceive it with the naked eye. In short colours are just the names we give to the parts of the electromagnetic spectrum that our eyes can perceive.
You got some great explanations already, but I want to add one thing that I find super interesting. There is a color hierarchy, which manifests linguistically. That’s to say that some languages only have 2 words for colours, some 3 words, some 20. So where we would say red is different from orange, a language that only has two or three words for colours would call orange “red” as well. They do see all the same colors as we do, but they just group more of the colors together under one name.
This is also because color is relative: something can look blue next to something white but then when you hold it next to something “even more blue” you can perceive it as actually more green.
What makes this even more crazy and interesting is that hierarchy, because it’s a specific order. Languages that only have 2 words for color, only specify black or white (or dark and light). So yellow would for example fall under light/white. If a language has 3 words, it’s always black, white and red. If it has for words, it’s always black, white, red and if I remember correctly blue. So there is not a single language that has only 3 words for colors and it’s red, blue and green.
Isn’t that cool!?
Because we know how colour vision works, and there are no gaps in the colours we can normally see. We have three types of colour receptors in our eyes. We talk about them as being for red, blue and green light, but they’re all three sensitive to a spread of wavelengths, and those spreads overlap. That means that if our eye gets ANY combination of wavelengths (within the visible spectrum), our brain gets a characteristic combination of signals from the three types. That combination is what we call a particular “colour”. So – there are NO wavelengths, or combinations of wavelengths (within the visible spectrum), that our brain doesn’t see as a colour.
Three things need saying.
Firstly, there are longer and shorter wavelengths that our eyes simply aren’t sensitive to. We can detect them with instruments; we can even use technology to let us see with them (eg heat-sensitive cameras, which are picking up infrared light and putting it on a screen as something we can see). But they don’t trigger the receptors in our eyes, so we don’t see them (in the case of ultraviolet, our blue receptors can actually pick it up, but it’s high energy and damaging, so the cornea filters it out; people who have to have corneal replacements can sometimes see it).
Secondly, not all animals have the same colour receptors as us. The colour world looks different to a dog, or a bee, and some flowers (for example) have markings on them in colours that we can’t see, but many insects can.
Thirdly, our eyes can be tricked. Your TV does it all the time. It doesn’t display, say, a “real” yellow. But true yellow is in between green and blue on the spectrum, and true yellow light will stimulate the green and blue receptors by different amounts (say, for argument’s sake, twice as much green signal as blue). So if, instead, you give your eye some pure blue light and twice as much pure green light, your eye sends the same signal to your brain as for pure yellow. So that’s what a colour TV does. Three sets of pixels matching the three colours our eyes are sensitive to. Colour TV is basically a trick tuned to the human eye – the colours won’t necessarily look right to other animals.
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