How many colours were there in a medieval rainbow? | Hacker News Reader

How many colours were there in a medieval rainbow?

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62 pointsprismatic55 comments

This is your reminder, should you want to go off the deep end into Sapir-Whorf linguistic relativism, that peoples whose languages did not have words to linguistically distinguish certain colors (such as blue and green) nonetheless demonstrably produced works (such as textiles) with patterns which required the ability to visually distinguish those colors, and that the strongest evidence we know of suggests merely that having a word for a color helps you to recognize it more quickly than if you don't have a word for it, rather than toggling whether you are capable of perceiving it.

Thanks, that's for me, your position ties with what I've read about cognition recently, that when we use a new word, it's like a shortcut for the brain, the more we use a word, the more the shortcut is reinforced. There was also that bit about Homer describing the sea as the same colour as wine, here's a good tear down of that http://www.abc.net.au/radionational/programs/bodysphere/feat...

I agree. I’ve always felt that they could see the difference in color immediately, just not readily be able to describe it to others.

I find our own modern ROYGBIV odd, with R=red O=orange Y=yellow G=green B=blue I=indigo V=violet

More sense would make: ROYGCBV with C=cyan (or replace the V with P from purple)

The "indigo" and "violet" are so similar to each other (and even a physically narrower band in the rainbow), while something is missing between the green and blue.

I know that it's an analog transition of colors so there are infinite shades and using 7 discrete names does not match reality, but when we do use names they should at least match popular language usage and uniform distance better imho.

Maybe it's subjective?

There are studies that has show that people can distinguish a color faster and better if their language has a word for it. If we assume this is true, your version would work better for english in particular. I suppose that more people can make a difference between green and cyan and blue and cyan, rather than between blue and indigo and violet and indigo.

Personally, I do not actually know what indigo is supposed to look like and an image search shows everything from blue to violet.

The Gamecube is indigo.

Nintendo may have called the purple version of the Gamecube Indigo, but Indigo is a dark blue dye derived from a plant, unless you think your blue jeans match your GameCube

They're just names for arbitrary divisions of the spectrum of vibrating matter around us. The HN top bar is still orange even if it's not the same color as the fruit. My GameCube is close enough to the color of the dye that I'll allow it. It's also a long way from purple.

I'm sorry but the "Indigo" GameCube is much closer to a strict definition of purple than it is darker blue https://en.wikipedia.org/wiki/GameCube https://en.wikipedia.org/wiki/Purple

I'm talking about my actual GameCube sitting in my game storage drawer, which I checked before making that comment. That image is much brighter and much more purple than the real thing I had in my hands.

Not entirely arbitrary - some of these colors(single-frequencies) match fairly well what one of our types of cone cells can easily detect, and some don't. Some frequencies are well-detected by two of the types of cones not just one, providing us with better ability to discriminate amongst those frequencies.

The blue-green distinction is interesting because it's different in East Asia:

* https://en.wikipedia.org/wiki/Blue%E2%80%93green_distinction...

The color of a traffic light can be referred to as blue or green. This sometimes leads to interesting translations where the color 青 can be translated as green or blue (eg 青茶 being translated as "blue tea" in Taiwan instead of "greener oolong tea" or something).

It was Newton that originally named ROYGBIV. Historically the word "blue" would have referred to a cyan colour, and "indigo" to a deep blue. So in fact you and Newton agree with each other, and the apparent difference is just due to semantic drift.

My kids will tell you there are six colors in the rainbow, that's what they were taught in kindergarten. The three additive primary colors and their secondaries. (Although they'll give you the name)

Makes more sense than choosing the number for biblical reasons I guess. Secondary colors are dual frequency colors, but the rainbow is made solely of single frequency colors, so that's wrong too. And purple/violet is just weird, the eye thinks the bluest blue has some low frequency red in it due to its response curves.

> Makes more sense than choosing the number for biblical reasons

The Bible doesn't say there are seven colors in the rainbow. Isaac Newton said so, to match the seven notes of a musical scale.

I agree with your kids. There are six: red, orange, yellow, green, blue, and purple. In grade school, I heard indigo and thought, who says indigo? You might as well add chartreuse.

You aren't alone in this sentiment:

https://blog.xkcd.com/2010/05/03/color-survey-results/

First, a few basic discoveries:

Indigo was totally just added to the rainbow so it would have 7 colors and make that “ROY G. BIV” acronym work, just like you always suspected. It should really be ROY GBP, with maybe a C or T thrown in there between G and B depending on how the spectrum was converted to RGB.

Hannah Smithson at Oxford has a beautiful research programme looking at medieval descriptions of rainbows and their relation to modern color spaces: here's an example that combines scholarly study of illuminated manuscripts and data from the Hubble Space Telescope. https://www.psy.ox.ac.uk/publications/464345

Interesting additional fact: 'rainbows' are not the same thing as the pure spectra that you might get from a prism.

To me and my Theology/Philosophy Education I would say that this is a difference between Aristotle and Plato. Up to the 16th Century the king of everything Science in Europe was Aristotle and their was always tension between the two philosopher's theories. https://www.diffen.com/difference/Aristotle_vs_Plato

People's worldview were more important than simple observation and is the biggest difference between modern science and the past, arguably. Isaac Newton even decided the 7 colors due to his own theory of the world. "Music and the Making of Modern Science. “It has no justification in experiment exactly; it just represents something that he’s imposing upon the color spectrum by analogy with music.” https://www.the-scientist.com/?articles.view/articleNo/48584...

Whenever I read articles like this I think it is Aristotle's forms and it is 100% why there are four colors.

From the article

> The reason why the author saw four colours in the rainbow comes from the theory of the four elements, an idea which goes back to Aristotle. But why those particular colours?

The answer to me is obvious. The "scientifically" held fact was the rainbow had four colors, because the rainbow represented the four elements. Now however you wanted to divide up the four colors was the scientific aspect of thought back than.

I find that the Plato vs Aristotle is not common knowledge in our modern times and causes a lot of people to view the people of history as idiots because we look at the rainbow and of course there are more than 4 colors. But they added "black" or "white" to add their 4th.

> going off of unique frequencies, there are more colors in a rainbow than there are stars in the Universe or atoms in your body,

Anyone better versed in optics than me care to write this in scientific notation? I know energy is quantatized and the visible spectrum is bounded, so there has to be a total amount of wavelengths, right?

>I know energy is quantatized and the visible spectrum is bounded, so there has to be a total amount of wavelengths, right?

It's only particles in bound systems that are quantized. For examples electrons in an atom can only have particular energies. But a photon from a rainbow is just flying through free space, so I think it can have any frequency.

Blackbody radiation emits photons in an uniform distribution, so the wavelength can be any real in the range.

Light comes in discrete energy quanta; a monochromatic light source with frequency f will come as one hf photon, two hf photons, three hf photons, and so forth because of the relationship E=hf, where E is the energy and h is Planck's constant. Multicolour light will come in different frequencies, but for each frequency there will be an integer number of photons. You will never see a photon with energy 1/2 hf or 3/4 hf, where f is that photon's frequency.

Frequency itself is not quantized; in the visible spectrum photon frequency can take on any real value between about 430 and 770 THz.

Moreover, frequency observer-dependent. Two observers related by a Lorentz boost (i.e., moving uniformly such that there is a constant relative velocity between them) will see the same photon with a different frequency (and thus by E=hf, a different energy); this is the relativistic red shift (or blue shift).

"Isidore’s encyclopaedic work De natura rerum asserts that there are"

- but "De natura rerum" is Lucretius's poem

- Isidore of Seville's encyclopedia is "Etymologiae"

- "De rerum naturis" (De Universo) is Rabanus Maurus's encyclopedia

what is the correct one?

(answering to myself) "De natura rerum" seems to be also the name of a part of Etymologiae (TBC)

There are 6 colors in the typical computer HSV rainbow. https://visual.ly/blog/wp-content/uploads/2012/04/RainbowEdg...

At least that's what I see if you uniformly vary hue and display it in the usual sRGB display. (7 bands, red is repeated). That's why naive rainbow visualizations are such a bad idea and visualizations should use perceptual color scales instead. For

Caveat: these perceptions are culturally relative. I'm born and raised in the US.

People were mad when Pluto got demoted. Can you imagine the riots if orange lost its status?

A great book that discusses this and a lot of other cognitive categories is George Lakoff's _Women, Fire, and Dangerous Things_.

Highly recommended for everyone that makes things that use categories, tags, criteria, &c.: https://en.wikipedia.org/wiki/Women,_Fire,_and_Dangerous_Thi...

Colour perception is indeed fascinating. My son is autistic, and his attachment of labels to colours is idiosyncratic - e.g. one of his favourite things is an Angry Birds pig plush, which he insists is "yellow". This makes complete sense to me once we mentally translate to a different classification scheme - I believe he is seeing the (classical) Greek "khloros", the vibrant colour of growing vegetation, for which we don't have a precise word in English.

What? That kind of green is clearly a yellowish green, like the Greek nymph. But what does that have to do with "different clarification schemes"? You seem to be implying that your son's scheme is aligned with that of the ancient Greeks, but I'm not seeing it. Could you elaborate?

An in-depth analysis of basic color terms across languages:

https://www.amazon.com/Basic-Color-Terms-Universality-Evolut...

(Noting that different languages do have differing numbers of basic color terms.)

https://en.wikipedia.org/wiki/Color_term#Basic_color_terms

Is there any colour (by hue) not in the rainbow?

Pink is considered to be a color not in the rainbow.

http://aschoonerofscience.com/science-communication/the-phys...

I’ve seen this before and am still bothered by the color name chosen. Is calling magenta “pink” a British (or Australian) thing maybe? Pink is a pale red. [1] Magenta isn’t pale red. Even the color wheel used here doesn’t label it pink. Where does this come from?

But yes, it’s interesting to learn that there is no wavelength for magenta.

[1] https://en.m.wikipedia.org/wiki/Pink

I think it's a British thing possibly, we have a children's nursery rhyme that includes the colour pink so that might be the reason as we just get used to calling it pink as a kid.

That wiki page says the Odyssey is written in approximately 800BCE. It looks more violet than pink to me.

I don't know about 'by hue' but almost all colors are not in the rainbow. The spectral locus is a line that runs around the edge of a 2D color space (technically 3D if you include luminance as well...).

7D if you are a mantis shrimp.

> 7D if you are a mantis shrimp.

Don't be sure:

* https://www.popsci.com/blog-network/ladybits/mantis-shrimp-v...

* https://phys.org/news/2014-01-mantis-shrimp-vision-different...

Though they do see polarization, which is a neat feature.

The pure purples are not in the rainbow because they are a mixture of red and blue, whereas the rainbow is made of single-frequency colors.

"The four created things in which all earthly things exist are aer, ignis, terra and aqua. Aer is air, ignis is fire, terra is earth, and aqua is water."

They actually weren't too far off. Sure, we have many more elements than just four, but there are only four states of matter. Although of course fire isn't literally plasma, but in a sense, they had essentially grasped this truth about these four fundamental states

There are more than four states of matter, but it’s true only the classical four would have been observable to a medieval person, so that is an interesting parallel.

There are no four classical states of matter. Nor, relatedly, would plasma have been observable to a medieval person. What parallel?

People could see lightning (which so far as I know, is a form of plasma) in the Middle Ages and relate it to the element of fire, no?

That is possible. However, the plasma state of matter cannot actually be observed (by a medieval person, etc.). How would they have determined that lightning, which is visible as a glowing plasma, does represent a state of matter different from solid / liquid / gas, but fire, which is visible as glowing, does not?

If you're willing to grant that they can't, then in what sense is it possible for them to observe plasma?

Don't be pedantic. So what if fire isn't plasma. They categorized the world by states of matter, but in a way which is not exactly parallel to modern people. Acknowledging that there world is made of mixture of fundamental elements was a great scientific achievement, even if it was wrong about how it worked.

GP isn't being pedantic, although I believe there was a significant misunderstanding. I think that ramchip meant fire, earth, air, and water, when he said "four classical states of matter, where as GP thought he meant solid, liquid, gas, and plasma.

>> So what if fire isn't plasma. They categorized the world by states of matter

> I think that ramchip meant fire, earth, air, and water, when he said "four classical states of matter"

That was the best interpretation I could come up with too. I wasn't saying fire isn't plasma, though of course it isn't. I was saying fire is not a state of matter. "They categorized the world by states of matter" is not correct.

For example, the ancients were well aware that ice was a form of water, not a form of earth.

since fire is not a state of matter, they were incorrect in what they admitted to their category of the various states of matter, but they still categorized fire as a state of matter and as such categorized the world by states of matter.

The interesting part was supposed to be that they came, with their categories relatively close to the actual classical categories - however I suppose that the classical categories were actually intellectually derived from (or their conception inspired by) the ancient 'elements'.

> they were incorrect in what they admitted to their category of the various states of matter, but they still categorized fire as a state of matter and as such categorized the world by states of matter.

No they didn't. Why do you say so?

They could just look at the sun. The stuff you see is mostly plasma.

Aristotle didn't consider the sun to be related to fire at all. As a celestial object, it would have been composed of ether.

> There are no four classical states of matter.

Gas, liquid, solid, plasma. I don't think this is very controversial?..

https://en.wikipedia.org/wiki/List_of_states_of_matter#Class...

The parallel is that each of the "elements" corresponds to a different state of matter.

Plasma would have been observable via fire.

Ah, you've found an error on my part. I was thinking "classical states of matter" referred to the understanding of states of matter in the classical period, which could not have included plasma. Again, plasma is not observable via fire, because fire is not plasma.

I think the question of fire is a lot less clear cut than you give it credit. See e.g. the discussion in https://physics.stackexchange.com/a/75106

But what of the Chinese elements? Wood, earth, metal, fire, water.

It seems like they didn't really classify it by solidness but just things that seem most abundant.

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