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### How many colors does a rainbow have?

by ambrus (Abbot)
 on Jan 24, 2009 at 12:35 UTC ( #738673=poll: print w/replies, xml ) Need Help??

vote on How many colors does a rainbow have?

 2 24/3% 3 24/3% 4 11/1% 5 26/3% 6 58/6% 7 461/49% 8 33/4% 9 15/2% 10 14/1% \$other 275/29% 941 total votes
Replies are listed 'Best First'.
Re: How many colors does a rainbow have?
by wilsond (Scribe) on Jan 24, 2009 at 20:02 UTC

"ROYGBIV" as taught in school. But if you're wanting accuracy, I'd claim some number near infinity.

 While I ask a lot of Win32 questions, I hate Windows with a passion. That's the problem with writing a cross-platform program. I'm a Linux user myself. I wish more people were. If you want to do evil, science provides the most powerful weapons to do evil; but equally, if you want to do good, science puts into your hands the most powerful tools to do so. - Richard Dawkins
Can you give an example of a number near infinity?

xoxo,
Andy

220 (C-class) - close to Infinity

350 (SLK) - greater than Infinity

1 rainbow = infinity - 1

When I was a kid we always said "red, orange, yellow, green, blue, purple", but of course there are a lot of transitional shades in between. I'd count indigo as one of those, since it's not a very well-known color by name. In fact, I've never heard of it at all outside the context of rainbows. Nothing is ever described as being indigo in color. If you're going to list indigo, you may as well include spring green, cyan, periwinkle, aqua, teal, fuschia, and chartreuse while we're at it.

--
We're working on a multi-year set of freely redistributable Vacation Bible School materials.
Nothing is ever described as being indigo in color.

Apart from the eponymous SGI workstation of blessed memory.

"We're working on a multi-year set of freely redistributable Vacation Bible School materials."

What exactly does that have to do with Perl?

Jeffery

Nothing is ever described as being indigo in color.

The Dinosaur Whiteboard strip 569 gives a counterexample.

Chemists Ferdinand Reich and Hieronymous Richter named indium after its indigo spectral lines.
Re: How many colors does a rainbow have?
by toolic (Bishop) on Jan 24, 2009 at 13:22 UTC
depends on the resolution of your detector :) 8-bit is 256 "colors", etc...
I thought it only had 6 colors not 1,000,000,000,000. Mike
Re: How many colors does a rainbow have? (8)
by tye (Sage) on Jan 25, 2009 at 06:17 UTC

I voted 6 because I never saw the point of separating "Indigo" and "Violet" (and ROYGBP maps nicely to three primary colors plus three secondary colors).

Then I searched around for some decent pictures of real rainbows. At first this confirmed my previous impressions; they all looked like they went from "Blue" to "Purple" then ended.

They also ran quite suddenly from "Red" to "Yellow" making "Orange" rather hard to pick out while "Green" through "Blue" were clearly not sufficiently represented in "ROYGBIV".

After reviewing several pictures of rainbows in the sky and from prisms, the best list of colors I could come up with was: Red, Orange, Yellow, Green, Teal, Cyan, Blue, Purple. The only picture that gave me an impression of separating "Purple" into "Indigo" plus "Violet" was http://people.rit.edu/andpph/photofile-c/prism-DSCN4982.jpg. Perhaps it is just that "Violet" tends to be quite faint.

Update: Then I went to look for cannonical examples of "Indigo" and "Violet" and found confirmation of my first point:

Although traditionally considered one of seven divisions of the optical spectrum, modern color scientists do not usually recognize indigo as a separate division and generally classify wavelengths shorter than about 450nm as violet.

This was immediately followed by something that was educational to me:

Indigo and violet are different from purple, which cannot be seen on the electromagnetic spectrum but can be achieved by mixing mostly blue and part red light.

Which rather reminded me of the term "monkey". Practicing biologists know that humans and (other) apes are not monkeys while non-biologists know that apes are a type of monkey (as are humans). I know that the color at the end of the rainbow is a shade of purple, despite what practicing spectrumists might believe. :)

Update: Actually, "Green" is still insufficiently represented. ... Yellow Lime Green Teal Cyan Blue ... seems more accurate. (Leprechauns++)

"Rainbows Only Yield Gold To Cannabis-Burning Potheads" - tye

http://en.wikipedia.org/wiki/Visible_spectrum would give 6 colors,
http://en.wikipedia.org/wiki/Rainbow would give 7 colors ...

In the rgb theory the prisma could also have 6768-1 colors, refered to http://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Spectre.svg/744px-Spectre.svg.png

I've just been counting the colors in the visible spectre image below, 6768 colors including the black waveline... but I think I'm just pulling the line a bit too much now ;)

Personally I think infinity-1, with 7 distinct visible differences.

I saw a great video once about how Blue & Red form purple. Basically that it's an imaginary color or some such made up by the brain.

"The Mystery of Magenta"

Not trying to advertise content or what not, so I guess I'll leave it to you to search it out.

But I found it interesting.

Basically something about how we're connecting 2 ends of the color spectrum by going the OTHER way.

Re: How many colors does a rainbow have?
by Illuminatus (Curate) on Jan 26, 2009 at 14:26 UTC
• Dog: 1
• Engineer: "Depends on detection range of your analyzer, and the wavelength gradient that it can individually distingush"
• Fashion Designer: "Depends on what they are wearing in Paris this year"
• Buddhist: "If a rainbow forms in the sky, and no one sees it, does it have any colors at all?"
• Acid User: "Dude, I smell at least 4, and can hear about 6 more"
• Salesperson: "Our next model will have 3 times the colors. I can send you a beta"
• Cosmologist: "Red, if the emitting object is receding at very close to the speed of light"
• Lawyer: "(after closing the shade and locking the door) How many do you want there to be..."

I'm in town all week...

fnord
Politician: Seasonally adjusted, it's in line with our predictions. But if you vote for the other party, all our good work will be undone. They would £\$%^ Carrier Lost

Regards,

John Davies
Re: How many colors does a rainbow have?
by zentara (Archbishop) on Jan 24, 2009 at 17:49 UTC
Re: How many colors does a rainbow have?
by rcaputo (Chaplain) on Jan 25, 2009 at 01:42 UTC

All of them! :)

That's actually not true. For instance red and blue are at opposite ends of the spectrum, so you don't get red + blue without green anywhere. That color is pink, and if you look you will see that it does not appear.
I have fond memories of pink.

A customer's newspaper had spot red but they often used pink in their design and therefore three plates were output instead of two - useless. "Don't use pink, we haven't got pink. What you think is pink is 50% red, use that instead." The other 50% being white.

We referred to pink as a tint, A hue produced by the addition of white.

Also, the colour was named after the flower, not the other way around. Pink described the frilly edges as in pinking shears.

One cannot expect the naked eye (especially from a distance and through an imperfect picture) to see or not see specific colors or even all of the colors hidden in a rainbow.

I found this:

(PhD physicist responds) The eye perceives six colors in the rainbow. Red, orange, yellow, green, blue and violet. (some people include the violet color of Indigo as a separate color.) But there are also colors in the infrared and ultraviolet present as well. The rainbow is caused by diffuse refraction of sunlight in water droplets. The source of the light is the sun's photosphere. While each atom in the photosphere may emit light at one quantum frequency, the sun is so hot that doppler shifting of the light causes the lines to "fuzz out" so that you see essentially a continuous spectrum of light. The strictly correct answer, would then be, "an infinite number".

I also found Physics in the Arts By P.U.P.A Gilbert, Willy Haeberli - Page 27. I found that to be pretty interesting.

_ _ _ _ _ _ _ _ _ _
- Jim
Insert clever comment here...

Re: How many colors does a rainbow have?
by CountZero (Bishop) on Jan 24, 2009 at 23:34 UTC
A digital rainbow has 111 colors.

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

Re: How many colors does a rainbow have?
by Moriarty (Abbot) on Jan 25, 2009 at 09:48 UTC

I have heard it said that men only know 6 colours, and since I'm a man, there could be no other answer for me.

Re: How many colors does a rainbow have?
by massa (Hermit) on Jan 26, 2009 at 15:36 UTC
2.3125 × 1028:
```#!/usr/bin/perl
use strict;
use warnings;
my \$red = 750e-9; # meters
my \$violet = 380e-9;
my \$distance = \$red - \$violet;
my \$planck_length = 1.6e-35;
my \$distinct_colors = \$distance / \$planck_length;
print "There are \$distinct_colors distinct colors\n";
[]s, HTH, Massa (κς,πμ,πλ)
Re: How many colors does a rainbow have?
by belg4mit (Prior) on Jan 24, 2009 at 23:57 UTC
6: R, O, Y, G, B + pinkish purple

--
In Bob We Trust, All Others Bring Data.

Re: How many colors does a rainbow have?
by adamcrussell (Hermit) on Jan 25, 2009 at 02:05 UTC
All I remembered was that the colors could be remembered via the "name" Roy G Biv...I let my laptop do the counting. :)
```\$ echo roygbiv | tr -d "\n" | wc -m
Or for much nicer perl powered output:
```\$ echo roygbiv | perl -e '\$a=<STDIN>;chomp \$a;printf "There are %d col
+ors in the rainbow.\n",length \$a'
Re: How many colors does a rainbow have?
by templar (Chaplain) on Jan 25, 2009 at 18:42 UTC
Sir Isaac Newton decided there were seven colors in a rainbow. I'll stick with him. He was right about gravity.

Actually, he wasn't right about gravity. That's why we have General Relativity, which may also be flawed because it doesn't work at the quantum level.

Or something. For everything I do, Newtonian Gravity is a good enough approximation.

Information about American English usage here and here. Floating point issues? Please read this before posting. — emc

I caught a show on Nova called The Elegant Universe a few years ago that shows where previous General Relativity and Quantum Theory are being attempted to be explained within a unified "String theory". Basically, as I understand it, Newton and Einstein (and others) only accounted for a fraction of physics that they could observer/were aware of. Newton had no idea about quantum mechanics because it wasn't a reality in his day. After Einstein came out with general relativity, he realized general relativity only governed large objects and realized his equations fell flat on the quantum level and died trying to account for his "theory of everything".

Today, String theory is trying to come up with equations which attempt to approximate Einsteins general relativity equations when describing large objects, Newtons gravity and quantum theory (as well as more odds and ends) for small objects into a single theory for all of physics.

I suggest looking for a better visual aid than The Elegant Universe if you're like me and prefer flashy pictures instead of reading books. The show itself and the guy who hosts it, Brian Greene, are a little heavy on the dramatics but are light on the more interesting details.

Although several String theories exist, to indicate the physicists still have their work cut out for them, but they seem to settle on a possibility for ten dimensions. I had a hard time imagining ten dimensions before, but a luck of turn would happen and I found an author who wrote a book amazingly titled, The Tenth Dimension and a piece of animation on the books' website which instructs in plain examples how to imagine all ten dimensions. Given my previous aversion to reading books, I was left with watching the animation and after numerous views I could follow the display all the way through.

"The three principal virtues of a programmer are Laziness, Impatience, and Hubris. See the Camel Book for why." -- `man perl`
Re: How many colors does a rainbow have?
by cdarke (Prior) on Jan 26, 2009 at 14:04 UTC
Unfair. I would have to go to the USA to count the colors, here in the UK we only have colours.
Re: How many colors does a rainbow have?
by ack (Deacon) on Jan 27, 2009 at 16:19 UTC

I think, if I remember my college physics on light, that theoretically it has an infinite number of colors...well...almost infinite.

It presents to the viewer all the frequencies that are in the light illuminating it that aren't obsorbed by the intervening atmosphere from the rainbow to the viewer.

That, of course, is not truly infinite...just a whole lot...way more than 10 which is the highest value in the survey except for 'other'. We just tend to 'see' the more limited banding which makes it seem like there are only a few colors.

On the other hand, when I look at a rainbow I rarely, if ever, am thinking about 'How many colors do I see?' I am thinking about how powerful, emotionally, the colors energize my feelings. Rainbows are a very powerful experience for me...quells the geekier sides of my personality. ;-)

ack Albuquerque, NM
Re: How many colors does a rainbow have?
by swampyankee (Parson) on Feb 01, 2009 at 15:19 UTC

Of course, I'm tempted to say "42," but will resist the temptation.

I wonder if the number of colors (or colours or χρώματα or 색깔 or 颜色) one sees in a rainbow is as much cultural as it is physiological. See, for example here or here.

Information about American English usage here and here. Floating point issues? Please read this before posting. — emc

Re: How many colors does a rainbow have?
by BrowserUk (Pope) on Jan 25, 2009 at 16:02 UTC
By that token maybe 4, because we also have separate receptors for brightness?

Oh, and I've heard there are people with some mutations who have pigments for two different shades of red, so they can actually see RRGB+brightness.

By that token maybe 4, because we also have separate receptors for brightness?

I don't think that you can classify intensity as a fourth "color".

If you increased the intensity of the spectural components in the rainbow whilst leaving their ratios unchanged, the observer would tend to squint, closing the iris, to reduce the overall amount light (number of photons), reaching the retina, with the result that the observer would perceive the same information.

Besides which, the rods only tend to come into play in low-intensity situations, when color information becomes distorted anyway. For example, at night, the green leaves of a rose tend to appear brighter than the red of the petals.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

"3" As in the others can be "synthesised" as a mixture of Red Green and Blue?

I thought it was Red, Blue, and Yellow.

Update: I obviously do not know what I am talking about :(

And you didn't even know bears could type.

Technically, isn't it that the colors are there (as actual separate yet overlapping ranges of wavelengths that partly trigger two or more sets of cones) but we make do with only three (usually) sets of cones to detect them since they trigger inexactly?

I'll ramble a bit, since the color spectrum is one of my favorite topics for thought experiments. I've used readmore tags so it's easy to choose not to look at what many of you might find boring.

Afaik, we know that healthy people have the same chemistry of colour-sensitive cells. I do not know nothing relevant about further signal-processing, I only know that the graphics or other professionals have common, healthy sight. They are just trained to distinguish more colours than we can name :>)

But, do not forget octarine

Re: How many colors does a rainbow have?
by jhourcle (Prior) on Jan 26, 2009 at 19:53 UTC
Re: How many colors does a rainbow have?
by chexmix (Hermit) on Jan 29, 2009 at 16:30 UTC
This poll ++. The discussions have made me smile.
Re: How many colors does a rainbow have?
by SilasTheMonk (Chaplain) on Jan 25, 2009 at 15:07 UTC
Well obviously the only way to answer this is to find a rainbow and count the colours. I always seem to be in a car and in a hurry when there is a rainbow sadly. Still it the answer is culturally relative as one might expect. wiki!
How many colors does a Prisma have?
by freakingwildchild (Scribe) on Jan 25, 2009 at 20:21 UTC
A Prisma device works the same as a rainbow does reflecting water and light....
Re: How many colors does a rainbow have?
by svenXY (Deacon) on Jan 26, 2009 at 09:44 UTC
a lot, but males can only see 16 (what is apricot, btw???)
Re: How many colors does a rainbow have?
by col (Monk) on Jan 29, 2009 at 12:49 UTC
Richard of York gave battle in vain. So that's seven.
Re: How many colors does a rainbow have?
by jgamble (Pilgrim) on Feb 03, 2009 at 00:35 UTC
I'm of the opinion that English has done a pretty good job of designating names for significant color differences, so I voted for the basic seven, and would not be dismayed by anyone who voted six. The indigo controversy does not phase me.
Re: How many colors does a rainbow have?
by deprecated (Priest) on Feb 03, 2009 at 19:45 UTC
Walter Lewin's Physics 8.02* course on MIT OCW explains exactly how many colors there are in a rainbow. And, really, it's far more complicated than you think.

* http://ocw.mit.edu/OcwWeb/Physics/8-02Electricity-and-MagnetismSpring2002/CourseHome/

--
Tilly is my hero.

Re: How many colors does a rainbow have?
by apl (Monsignor) on Feb 03, 2009 at 12:48 UTC
I remember reading a Start Trek novel many years ago (sue me) that said Klingon vision was shifted towards the ultra-violet end of the spectrum, so they saw the red end of the spectrum as 'Black'. That was why Star Fleet Security (the so-called 'Red Shirts') upset them so; they were all dressed in Death Black...

So I guess the number of colors in a rainbow depends on the species looking at it...

Re: How many colors does a rainbow have?
by ryanc (Monk) on Feb 03, 2009 at 23:52 UTC
There are 8 colors here in Discworld.
Re: How many colors does a rainbow have?
by ikegami (Pope) on May 12, 2017 at 05:55 UTC

It can have as many colors as it wants to have!

Re: How many colors does a rainbow have?
by BrowserUk (Pope) on Aug 09, 2011 at 05:44 UTC

If anyone else is like me and still fascinated by the depth of discussion this seemingly simple poll engendered, then find an hour to watch this BBC Horizon video (Do you see what I see?).

Assuming that the Beeb will let you view it from your location, it will also fascinate you, but be prepared to have your both your science and perception challenged.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
a rainbow has exsactly five colors

No it doesn't!

Re: How many colors does a rainbow have?
by sundialsvc4 (Abbot) on Feb 05, 2009 at 15:45 UTC

The human eye can see seven distinct colors, but by definition the entire spectrum is there.

Re: How many colors does a rainbow have?
by ambrus (Abbot) on Jun 26, 2009 at 11:19 UTC
Re: How many colors does a rainbow have?
by sandeepbharmoria (Beadle) on Feb 02, 2009 at 07:09 UTC
It Should be 7 !!!!
Re: How many colors does a rainbow have?
by gregor-e (Beadle) on Feb 05, 2009 at 21:33 UTC
```\$ wc -l /usr/X11R6/lib/X11/rgb.txt
753 /usr/X11R6/lib/X11/rgb.txt
```
An additional explanation perhaps would help!
Re: How many colors does a rainbow have?
by Xiong (Hermit) on Jul 25, 2010 at 20:16 UTC

Once, I saw a very rare triple rainbow, outside of Toledo, OH.

Note: Contents may change.

It's not so rare. We just don't look at the sky much, sort of like the Krikketers. Most of us (including me) probably can't tell what phase of the moon it is most of the time.

Re: How many colors does a rainbow have?
by Anonymous Monk on Feb 12, 2011 at 13:19 UTC
It has 7 colors.
in preschool taught 7 colors... its red orange yellow green blue purple pink.... there is no indigo and violet also....????? which is true???
Roy G Biv Red orange yellow Green Blue indigo violet
Re: How many colors does a rainbow have?
by Anonymous Monk on Jan 25, 2009 at 13:59 UTC
Wooof VIBYYYR

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