Things that are obvious once pointed out, but I never thought of on my own.

[xiphias]

The colors of the rainbow. How many are there?

Red, orange, yellow, green, blue, indigo, violet. Seven colors.

Do you see anything unusual about that list?

How many primary pigment colors are there?

Red, yellow, blue. Three.

How many secondary pigment colors are there?

Orange, green, purple. Three.

For a total of six.

How come we say "purple" for a mixture of blue and red, but split "purple" into "indigo" and "violet" for purposes of the rainbow?

Because Isaac Newton decided that there MUST be seven colors, because there are seven classical planets, seven notes in the classical scale, seven days of the week, and seven is just generally an important number. Therefore, there MUST be seven colors, and therefore, "indigo" and "violet" must be separate colors, and not just shades of "purple".

Because, if the facts don't fit your theories, the facts must be wrong.

Comments

[flouritephoenix.livejournal.com]

I teach kids. When I do my rainbow drama/song lesson plan, it's 7 weeks long. For the 7 colors of the rainbow:

Red
Pink
Orange
Yellow
Green
Blue
Purple

[caprinus.livejournal.com]

I already voiced my strong objection to purple on the rainbow below. But... this? Seriously? PINK is between red and orange? Have these children ever seen a rainbow?

I hope you might consider amending the lesson plan in the future. Butterfly drama/songs? Flowers? Birds?

[flouritephoenix.livejournal.com]

Do you know how many great children's books there are about the color pink? How could I not use pink?

Just Pink
Poodlena
Pinkalicious
The Pink Refrigerator

to name a few. And girls love pink. I'm not in the business of telling kids what to like.

I've got 4 solid themed lesson plans. Animals (12 weeks), Colors (7 weeks), Classic Books (12 weeks), and Fairy Tales (12 weeks). But only one lets the kids dress in the color of the week every week.

[caprinus.livejournal.com]

Oh, I agree pink is lovely, and that children of all genders may like it, and in no way am I suggesting you need to delete it from the lesson plan! However, you are in the business of teaching children the truth, I would hope, and if you teach them that there is pink on the rainbow they will be laughed at later on when they get to physics class and hear about Roy G. Biv. That is why I am suggesting birds, flowers, or butterflies -- the seven-week colour lesson plan can be based on all sorts of things! If you don't associate it with the rainbow I have no objections.

[flouritephoenix.livejournal.com]

They're 3-4 years old. I think they have plenty of time to learn the harsh realities of a pink-less rainbow. :-)

You'd be surprised

[shmuelisms.livejournal.com]

You'd be surprised how stubbornly children/adults stick to the "truths" they learned as a 4 year old. The things that "everybody knows", are the hardest to correct. A few years ago, I read a piece by a German professor of Biology, about how he encountered first year biology students that were certain that bees actually talked! This because they grew up on Maya the Bee, a classic book and TV series. He brings many similar examples. You'd think that 12 years of schooling before university would have corrected that impression. Apparently not!

Pyramids are really easy to draw, right, just a small number of straight lines and you're done? So of course, when teaching the Biblical story of the Exodus from Egypt, most preschool or lower grade teachers draw pyramids. It's then nearly impossible to convince older children or even adults, that the pyramids are completely irrelevant to the Exodus because they predate it by at least 500 years...

[ckd]

Also, Roy G. Bv decided he needed to buy a vowel.

[akaihyo.livejournal.com]

Well, I like indigo as a color, so I cannot say that it bothers me too much and, as ckd pointed out, it messes with the mnemonic. How would you pronounce Roy Gbp? But interesting to know the origin of the seven colors.

[fauxklore]

A friend told me the Chinese do it with 7 colors also, but use aqua (between blue and green) instead of indigo.

[cucumberseed.livejournal.com]

My support of Indigo as a color (and Pluto as a planet) was cemented in ninth grade by my earth science teacher who very smugly explained than neither were. Wonders that she didn't manage to make me hate science.

[gingicat]

I see indigo as a variation on blue, myself. And it does seem to have its own stripe, but maybe that's the power of suggestion?

[felis-sidus.livejournal.com]

Oh, good; I'm not the only one.

To muddy the waters a bit more, here's the Wikipedia entry on indigo.

[caprinus.livejournal.com]

The "stripe" effect is probably linguistically-motivated, our eyes being physiologically fairly weak at distinguishing the gradations in this end of the spectrum, and indigo not being a "peak"; but I agree it's a variation of blue. :)

[xiphias.livejournal.com]

I don't see ANY of them as having stripes. To me, it all looks like a continuous smoosh.

[theclamsman.livejournal.com]

This, because the "indigo" colored pencil we artists generally use (the animation artists use indigo for their sketches, too...as well as tuscan(?) red) is blue, not purple.

[gingicat]

Well, and the indigo plant is used to make dark blue dye.

[caprinus.livejournal.com]

We say "purple" for a mixture of blue and red. Correct. However, the rainbow IS NOT A COLOUR WHEEL. Where on earth do you see in the rainbow a place where red and blue are adjacent to each other??? I seriously just had a small aneurysm trying to visualise this. o_O

Mind you, this is some kind of a linguistic disconnect -- my wife shares your sentiment, and sees violet as a shade of purple, where to me it is no such thing. You're definitely not alone. But the plain fact is, the red wavelengths and blue wavelengths of the spectrum nowhere gradually transition into each other in the manner you are suggesting, the way that green is a gradual transition between blue and yellow. There is no purple in the rainbow however you slice the spectrum linguistically.

I do agree with you that indigo is an unneccesary intrusion of Newton's numerological prejudices (I've just watched a show on his work on Biblical prophecy and calculations of the date of Armaggedon (2060) -- he was not the pure rationalist people take him for). He should have stuck with basic colour terminology, and thus six colours. However, not the six colours of the colour wheel, which is trying to impose another set of assumptions on the fact of decomposed white light.

edit: Something else just occurred to me -- when you ask, "do you see anything unusual about that list?", another answer would suggest itself to, say, Chaucer, or anyone living before 1542. "Orange? What is this invented colour we have never heard of between red and yellow?". There is no reason orange should be on the spectrum any more than indigo should (in fact, it predates orange by a few hundred years). Different cultures slice the rainbow up into different bands. It's all arbitrary to a degree (although human physiology does privilege certain wavelength bands across cultures -- the "primary" colours).

This is for xiphias, too.

[metahacker.livejournal.com]

There is an odd effect at the blue end of the spectrum; your "red" cones are sensitive to blue light, too. Here's a good picture.

See that second hump in the red response, there? That's indigo. The part where that hump slacks off faster than than the blue? That might be Newton's violet.

More fun stuff: it may be that some humans have an additional type of cone.

Re: This is for xiphias, too.

[dancing-kiralee.livejournal.com]

Thank you. That finally answered one of my long standing questions about how we preceive light.

Kiralee

[dancing-kiralee.livejournal.com]

"Because, if the facts don't fit your theories, the facts must be wrong."

Unless they are definitions...

See, I'm with caprinus in thinking that the colors of light from a prism and colors of light reflecting off paint are two different things, created by two different, if slightly related, physical processes - both of which are, well, modified by the physical processes our eyes use to 'see' color.

So Newton, when he studied how prisms effect light, decided to arbitrarily break up the result into 7 different categories of color. He could have used 5, or 4, just as easily (I probably would have used 4, because when I look at a rainbow that's usually what I see - Red, Yellow, Green, and Blue). Given how people see, three might have made sense too; but he used 7, because he was also an alchemist, and that's what made sense to him.

Since he was the one who was defining the colors of the spectrum, he got to be the one who defined them.

It turns out that 6 is a somewhat more natural and effective choice; but that's far from immediately obvious. We only know that because we've had a few hundred years more of analyzing the science of light / color, and, in particular, how the eyes see it.

Newton wouldn't have been in a position to benefit from our knowledge; he had define some system of classification, and, all things considered, he wasn't that far wrong.

Kiralee

[holzman.livejournal.com]

There are no facts in play in the question "how many colors are in a rainbow?" For any color one names in a rainbow, there's a range of photon frequencies that produce light with that label. One can split that range of frequencies in half and call it two colors with equal legitimacy to Newton's seven.

wrong ended question

[(Anonymous)]

Shouldn't the question be "How many colors can our three color receptors distinguish in a rainbow..."?