'(The Blog) With No Name', perhaps best described as a stream of notes and thoughts - 'remembered, recovered and (sometimes) invented'.

Tuesday, September 27, 2005

The Riddle (?) Of The Rainbow

This is on a doubt I have had for most of my life so far.

Just like practically everyone else, I was told very early in life that the rainbow has 7 colors (and learned their names by rote). Whenever I see a rainbow, I try to count. It is far from obvious to the average eye (to the best of my knowledge, my color-vision is pleasantly average) that there are actually seven colors - it could very well be 5 or 6 - especially at the blue end, it is very hard to clearly discern the triplet (violet, indigo, blue). We talk about human color perception here, not the ACTUAL number of colors - scientifically, there is of course, a continuum of visible frequencies in sunlight and in the rainbow.

I don't think in Indian languages, there are even words for 'indigo', 'orange' ... but mysteriously it appears even in ancient India, the rainbow was said to have 7 colors. More mysteries - to self - here: Does Surya's (the Sun God) chariot have actually 7 horses and if so did these 7 represent the colors of the rainbow or something else? More basically, did folks here in India know that the rainbow came from a play of Sunlight (unlikely)?

Is it the case that in some culture, some folk-tradition, the rainbow has a different number of colors?

Note 1: And here is an intriguing bit from the online wikipedia article on the rainbow:

It is commonly thought that indigo was included due to the different religious connotations of the numbers six and seven at the time of Isaac Newton's work on light, despite its lack of scientific significance.

Well, that, if true, thickens the plot quite a bit!

Note 2: Probably, most Indian languages have names only for very few colors. It is more like the same word stands for a whole range of colors - 'Nila' in Sanskrit can be blue or dark-blue-tending-to-black or anything in the middle. Does this skimpy color vocabulary indicate a lack of sensitivity to colors and their nuances? I don't think so, but must say, in view of this limited set of names, it even feels 'realistic' to suspect the Indian tradition originally assigned not 7 but probably only, say, 5 colors to the rainbow ('Panchavarnam')!


  • At 10:22 PM, Blogger Sumesh said…

    Here's some light on the issue (from

    The Colors of the Rainbow

    Sir Isaac Newton in his early physics experiments decided the colors of the rainbow were Red, Orange, Yellow, Green, Blue, Indigo and Violet. Many of us remember them as ROY G BIV. Are there only seven colors? Newton believed in numerology and thought special numbers governed all natural phenomena. Seven is a very special number. There are seven days in the week, seven openings in our head, seven seas, seven continents and many other important sevens. So, of course he found exactly seven colors. In reality, the rainbow colors merge gradually into one another. Our eyes sort them into groupings. How many colors are in the rainbow? Anywhere from three to, as many as, several thousand. It depends on who is counting and what they believe is there. Funny how what we expect to see is often what we see.

    The color order of the rainbow, starts with red at the outer edge and moves through the colors to violet. The brightness and the width of the bands and colors may vary greatly in an instant of time while you watch a rainbow and are related to the size of the drops that form the bow. The colors at the base of a rainbow are different from those at the top. Most rainbows only contain red near the ground. It is very rare that red is seen at the top of the rainbow. The width of the bow measured from red to violet will be about four times as wide as the full moon.

    The rainbow's colors are like people, I have never known two to be exactly alike. To really understand the colors of the rainbow study them closely when they appear and come to your own conclusions.

  • At 6:29 AM, Blogger R.Nandakumar said…

    thanks, sumesh.

    so, the number of colors one can see on the rainbow is indeed a subjective thing. in hindsight, the post should have made it clearer that my primary question was a 'cultural' one - how many colors did the various cultures of the word assign to the rainbow (and well, was it Newton's numerological fixation which began a global standardization of their number)?

  • At 4:08 PM, Blogger Sunil said…

    Interesting post....but what is the number assigned originally in older Indian texts? I don't know.

    But i do know that Indradhanush (Indra's bow, or "rain" bow, since Indra was God of the rains) is darn similar to rainbow did that happen?

  • At 9:39 AM, Blogger Iyer the Great said…

    Quite a thought provoking post. Though sumesh's comment tells us why the 7 color's came into being, I am not totally convinced.

    Btw: the 7 horses in Surya's chariot represent the 7 days of the week.


  • At 2:36 AM, Blogger R.Nandakumar said…

    Thanks Rahul, for pointing out the week-horses connection.

    And thanks Sunil. No one yet has shot down my tentative guess that in ancient India, they saw only 5 colors on the rainbow!

    The 'Indradhanush' thing notwithstanding, the Rainbow was NOT seen as a bow universally - see the wikipedia article on the rainbow for a variety of myths; it is a bridge to some, a slit in the sky to others and... Perhaps, just as the Biblical and Indian myths made it into a celestial bow, those of the Australian aborigines could well have conceived of the rainbow as God's, well, boomerang!

  • At 7:57 PM, Blogger Myna said…


    I have seen a recent article on the web which was talking about ignoring Indigo from the seven colours. Reason: Indigo is difficult to distinguish with Violet and Blue.

    What we expect to see is often what we see, as Sumesh has rightly said. So is the case in literature or ancient books.

  • At 6:29 PM, Blogger Doctor Bruno said…

    What about considering rainbow as having 50 thousand colours :) ....... Of late, if any one hears the word color, he immediately remembers 50,000 (thanks to relentless marketing by RmKV)


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