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
It’s important to distinguish between the ability to sense light of certain wavelengths, and the perception of color. They aren’t the same thing – two colors can appear absolutely identical but be made from entirely different combinations of light wavelengths.
For example, ‘blue’ sapphires don’t look that way because they transmit only a narrow range of blue light. They actually permit most wavelengths of humanly-visible light to pass through them. But they absorb, and therefore subtract from white light, a narrow range of ‘yellow’ light. And we perceive white-light-minus-yellow as blue.
Color is basically the wavelength of light reflected from objects and interpreted by our eyes and brain. The wavelength part can said to be objective. (We also sometimes assign color names to wavelengths on the spectrum, like describing 650 nm as spectral “red”, but those namings are arbitrary.)
Colors themselves are not objective because they are produced by our brain as a response to sensations or a combination of them further filtered by our eye cones. We can safely say that all animals process color a bit differently. For example, your dog can’t actually watch TV the way you do, because TV screen emit light specifically in a way that’s easy for humans to perceive. Dogs have two photoreceptor cells in their retina, humans have three. When dogs look at a screen they likely see a lot of flickering, even if they may be smart enough to recognize some shapes as images.
One famous example you may have heard of, the difference between purple an violet. When the human eye perceives light at 400 nm, just below blue at the limit of our perception, it produces a color. When we see red and blue light together, it also produces a color. But, for some reason, due to some peculiarity or deficiency in our brains, these colors are the same. Likely many animals are able to see a completely different new color when they see violet, but for humans, when you show them a picture made with mixed violet and purple color, they can’t tell the difference.
Birds can see some ultraviolet light and many birds actually have some ultraviolet patterns on their feathers, but we don’t see them with just our eyes. Crows have UV colours but we see them as just black, pigeons have some UV colours but we see them as mostly grey with some shades of green and purple here and there.
If a red apple was also colored in some UV light, we would only see the red (just like we don’t see it in pigeons). If an apple was colored ONLY in UV light, it would look black to us (just like crows).
We can make cameras that see all kinds of “colors” we can’t – infrared, ultraviolet, microwaves, xrays etc.
We can also make filters in colors we can’t, like a filter that only lets infrared or UV light this.
So combine lots of filters at different wavelengths of light (“color”) with a camera that can see those wavelengths and we can find exactly what colors that objects reflect even all the colors our eyes don’t see.
The human eye has three types of colour sensitive cone cells in it, and they cover a range of light frequencies, with the combination of how strongly the cells activate allowing us to differentiate between a range of colours. Light, or rather the electromagnetic spectrum, comes is a huge range of frequencies, well beyond what we can see, and well beyond what we might consider to be light.
In addition to seeing with our eyes, we can make cameras that are sensitive to light, and can differentiate between frequencies using sensors that are sensitive to specific frequencies, and construct an image based on that. We can, however, make those types of sensors able to detect light at frequencies beyond the range that humans can see, and manipulate the output from those cameras to provide us with an image that we can interpret that incorporates frequencies of light not visible to humans.
An interesting real world example of this relates to bees and flowers. We know from careful biological study that bees can see further into the ultraviolet range than humans, and by imaging flowers with cameras sensitive to that light, we have found that some flowers that attract bees by being colourful are actually brightly coloured in the UV range, that bees can see but we can not.
There is a separate aspect to colour perception that relates to how the brain interprets what it can see. In fact a huge amount of what we think of as “seeing” things comes down to what goes on inside the brain, not in the eye itself. There have been interesting anthropological studies relating to how culture and language relate to the perception of colour. Not all languages have the same number of words for different colours, and not all languages distinguish them in the same way.
Anthropologists have noticed that the number of colour words a language has differentiate colours in a set order. If a language has just 2 colour words, they are dark and light (eg black and white). If there is a third, it is for red. Then either green or yellow, then the other of green or yellow, then blue, then brown, and finally purple, pink, orange and grey. But not every language groups colours in the same way. In English, we think of some colours as “blue and others as “green”. In Celtic languages, before English became a dominant influence, the word “glas” included some things that English speakers call green, and some things that English speakers call blue, but some green things an some blue things are also not “glas”, they are some other colour.
What is really weird, though, is it goes beyond language. There is an experiment where you show a person four squares. Three are the same colour and one is a little bit different, and ask the person to identify which square is the different one. If there person comes from a language and culture where the two colours fall on different sides of a division for colour words (say red and orange), they can identify the odd one out with a high degree of reliability. If you show the same colours to a person from a culture where the two colours are grouped as belonging to the same colour word, the ability of that person to pick the odd one out is very significantly lower. That suggests that the perception of colour is not just in the eye, but in the interpretation. The person who can not name the colours differently actually has a harder time being aware that they are different at all.
The human eye has three types of colour sensitive cone cells in it, and they cover a range of light frequencies, with the combination of how strongly the cells activate allowing us to differentiate between a range of colours. Light, or rather the electromagnetic spectrum, comes is a huge range of frequencies, well beyond what we can see, and well beyond what we might consider to be light.
In addition to seeing with our eyes, we can make cameras that are sensitive to light, and can differentiate between frequencies using sensors that are sensitive to specific frequencies, and construct an image based on that. We can, however, make those types of sensors able to detect light at frequencies beyond the range that humans can see, and manipulate the output from those cameras to provide us with an image that we can interpret that incorporates frequencies of light not visible to humans.
An interesting real world example of this relates to bees and flowers. We know from careful biological study that bees can see further into the ultraviolet range than humans, and by imaging flowers with cameras sensitive to that light, we have found that some flowers that attract bees by being colourful are actually brightly coloured in the UV range, that bees can see but we can not.
There is a separate aspect to colour perception that relates to how the brain interprets what it can see. In fact a huge amount of what we think of as “seeing” things comes down to what goes on inside the brain, not in the eye itself. There have been interesting anthropological studies relating to how culture and language relate to the perception of colour. Not all languages have the same number of words for different colours, and not all languages distinguish them in the same way.
Anthropologists have noticed that the number of colour words a language has differentiate colours in a set order. If a language has just 2 colour words, they are dark and light (eg black and white). If there is a third, it is for red. Then either green or yellow, then the other of green or yellow, then blue, then brown, and finally purple, pink, orange and grey. But not every language groups colours in the same way. In English, we think of some colours as “blue and others as “green”. In Celtic languages, before English became a dominant influence, the word “glas” included some things that English speakers call green, and some things that English speakers call blue, but some green things an some blue things are also not “glas”, they are some other colour.
What is really weird, though, is it goes beyond language. There is an experiment where you show a person four squares. Three are the same colour and one is a little bit different, and ask the person to identify which square is the different one. If there person comes from a language and culture where the two colours fall on different sides of a division for colour words (say red and orange), they can identify the odd one out with a high degree of reliability. If you show the same colours to a person from a culture where the two colours are grouped as belonging to the same colour word, the ability of that person to pick the odd one out is very significantly lower. That suggests that the perception of colour is not just in the eye, but in the interpretation. The person who can not name the colours differently actually has a harder time being aware that they are different at all.
The apple probably gives off light outside the visible spectrum, but we can’t see outside the visible spectrum, so it’s red.
Remember, light is the same thing as radio waves, microwaves, infrared, ultrviolet, x-rays, and gamma rays.
The apple probably gives off light outside the visible spectrum, but we can’t see outside the visible spectrum, so it’s red.
Remember, light is the same thing as radio waves, microwaves, infrared, ultrviolet, x-rays, and gamma rays.
Latest Answers