Graphic Design

Why does the Rainbow have 7 colors?

October 29, 2020 | 0 min read

Glorify

As we know, the rainbow colors are seven in number: Violet, Indigo, Blue, Green, Yellow, Orange, and Red. The best way to remember the rainbow color order is by its acronym ‘VIBGYOR.’ 

However, the teachers of elementary school tell us that there are three primary colors; Red, Yellow, and Blue that when combined make three secondary colors; Orange, Green, and Purple. Perhaps including the black and white paint that makes every other color imaginable concluding to be six basic colors. 

Rainbow have seven colors 1

Now, the color Purple if we see is then divided amongst itself into the color Purple and blueish purple. OK, so who decides that now? And, why do they? Well, let’s just keep it short and say ‘Issac Newton. Yes, the Ancient Greek philosopher. Wait, what?

The Theory of Color is a bit more complicated than just stirring together the finger into paints, so let’s get started already! 

The visual spectrum – Why Does The Rainbow Have 7 Colours?

Pigments are mixed using a well-known-understood-yet confusing subtractive method that uses red, blue, and yellow as primary colors. However, colors that we see are in light waves are combined according to the mixing method that uses red, green, and green as primary colors. 

The visual spectrum

Great! So how does Sir Isaac come into this? In the 17th century, he was one to realize that when a white light breaks apart and is looked through a prism or raindrops, it breaks into a visual colored light spectrum. In other words, the rainbow. 

In this visual spectrum, one can notice that each color bleeds into the neighboring color. For a rather surprising factor, it is not a distinct set of colors but a spectrum. So here, Sir Newton decided that probably by breaking this spectrum into chunks we could easily talk about the divisions. But then, how many divisions should there be? 

Ancient Greece and the magic of seven: Why Does The Rainbow Have 7 Colours?

Easy! Seven is a lucky number!

Or, for those in the western cultures have been so told. This is because of the 6th century BC and an (in)famous philosopher named Pythagoras. He loved numbers and also loved applying them to the phenomena of the real-world. He is known for discovering the seven musical notes that could be easily translated into mathematical equations for which he had a theory too. The theory involved how the seven heavenly bodies (known about at that time) moved according to the mathematical patterns. 

Do you notice a pattern? No? Well, Pythagoras did. The observation he made showed that seven was a magical number that connected to the disparate phenomena somehow. He then added that he saw it as the sum of that of spiritual and that of the material. 

Ancient Greece and the magic of seven

As he started school, his ideas espoused and grew into the philosophy that was called Pythagoreanism that was based on mysticism and mathematics! This theory was influenced by some of the most well-known classical thinkers which included Plato and Aristotle. 

And now we have seven days of the week, seven deadly sins, seven wonders of the world, seven liberal arts subjects, and seven dwarves.

So, how did it apply to the rainbow?

The circular route from Newton to Pythagoras: 

Philolaus, the Pythagorean philosopher was one of the first known to propose that the earth revolved around a ‘central fire’. This theory was known by Copernicus, who is credited for inventing the heliocentric theory of planetary motion. Newton further relied on Copernicus’ work while developing his own theory of gravity.

Newton acknowledged the Pythagoreans theory: Why Does The Rainbow Have 7 Colours?

The spectrum was originally subdivided into five colors by him (red, blue, yellow, green, and purple). He then revised the number to seven from five by adding indigo and orange as Pythagoras believed there was a strong connection between music and color. As there are seven natural notes there should be seven principal colors too.

Newton acknowledged the Pythagoreans theory

So all said and done: Due to math, numerology, music, and a few great men of the past,  there are seven colors in the rainbow today!

Why Does The Rainbow Have 7 Colours FAQs


1) Can you touch a rainbow?

A rainbow is a product of the reflection of light off the water particles in the air. You can touch water particles and the refraction if you believe you can touch light and view the rainbow.

2) Why don’t we have a black rainbow?

Since a rainbow is formed by the separation of light of its original combination of many wavelengths, and, black is no light, there cannot be a black rainbow.

3)Why are rainbows curved and not straight?

Rainbows are curved as the set of raindrops has the right angle between the sun, observer, and the drop that lie on a cone that points at the sun.
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