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
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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