Asking how many colors are in a rainbow is akin to asking how long is a piece of string. White light is split as it travels through a prism, typically raindrops, into a full spectrum of color that goes beyond what we can see.
But the exact number of colors in the rainbow isn’t purely based on science. However, their order is science-based. Why the discrepancy?
The main seven rainbow colors, in order, are:
The order is based on their wavelength, the shortest being violet and the longest being red. However, there are seven colors due to Pythagoras and Newton’s fondness for the number seven.
The conundrum of the rainbow’s colors has to do with language and perception. The spectrum of light in a rainbow remains the same. The wavelengths are measurable.
A color wavelength of 492nm will look very different from the color wavelength of 622nm. But is 492 really blue, or is it green? Is 622 red or orange. Where do these lines get drawn, and why? Some blame music, others mysticism.
7 Colors Of The Rainbow In Order
A rainbow’s seven colors are listed from the shortest wavelength the human eye can see (around 400 nm) to the highest (about 700nm).
These colors are often taught to children backward with the easy-to-remember name: Roy G BIV.
However, Sir Isaac Newton initially only saw five. Yet, it was he who gave them seven.
Why Do Rainbows Have 7 Colors?
Sir Isaac Newton is the physicist and mathematician credited as the person who understood the connection between rainbows and white light. He observed that rainbows resulted from light being split by a prism.
Thus, he was granted the privilege of influencing how we perceive the color spectrum known as a rainbow.
At the time, Newton was bound by the colors he could see. Colors outside the human spectrum, such as ultraviolet, had yet to be discovered. Thus, Newton observed:
But Newton was fond of Pythagoras, who was, in turn, drawn to mysticism. For Pythagoras, numbers had power and symbolism. Numbers were in nature and music if only you looked for the patterns.
Thus, in our modern world, we do. Take music that revolves around seven notes:
Thus, Newton added two colors: indigo and orange. Now the rainbow was as balanced as a musical scale.
However, most Westerners do not see colors the same way as Newton. Or, more accurately, we do not always use the words attributed to colors in the way Newton understood them to mean.
Why Newton’s Blue Is Probably Not Your Blue
Color is a spectrum. We know this in art. However, the answer isn’t straightforward when asked, “What colors make orange?”. This is because orange comes in a wide range.
Thus, mixing Burnt Sienna with Cadmium Yellow will produce a different orange than Cadmium Lemon with Cadmium Red.
This is the difficulty scientists have when translating color wavelengths into languages like English. A color wavelength can be measured and assigned a number.
Any debate if that wavelength is 650 or 670 nm can be settled by getting out the tools and taking a reading.
However, color becomes less scientific when we label it based on what we see. Thus, Newton’s blue may not be precisely how blue is perceived today. What Newton thought of “blue,” he was describing a blue-green that is often associated in our modern world with the words “teal” or “cyan.” If we were to show Newton what we call blue, he’d probably call it “violet.”
This discrepancy between perceptions of colors has led to indigo being pulled into a debate.
Why Indigo Is A Controversial Rainbow Color
Just as there are roaring debates over Pluto’s planetary status, some want to kick indigo out of the rainbow. There is the fact that Newton only added it to help reach the all-important seven.
But the main thrust of the indigo-go argument is that most people cannot differentiate between indigo and violet when looking at a rainbow. To the modern eye, it’s typically all one strip.
However, perspective shifts when a person considers that part of the blue we see as blue was, to Newton, violet. That thin band we struggle to split into two different colors is significantly wider if the blue band creeps up closer to green.
Then again, how much does the debate matter when we know rainbows have far more colors than we can see?
How Many Colors Are In A Rainbow?
It is easier to ask what color frequencies are in a rainbow than colors. Seven official visible colors, ultraviolet light, and infrared, are sitting beyond our visual recognition.
These waves still pass through our eyes, but our receptors and, consequently, our brains can’t “read” them.
But how we see and perceive color is as much about how our eyes are designed as our language. For example, black isn’t color as it pertains to light. Black is the absence of light.
But in art, black is a color. In a way, it could be argued that black is the artistic equivalent to white light: many colors in one. Our human perception has us using the same word, black, for two very different things.
Thus, color in a rainbow is about how many names we wish to give the wavelengths. Science currently has ultraviolet boundaries of 10nm to infrared at .01cm.
When you go past ultraviolet, you hit x-rays, then gamma rays. On the other side of the color wavelength spectrum, you leave infrared and hit the radio waves, such as radar.
If you ignore the debates about where you draw a line between color wavelengths and x-rays, you are left with a span of 10nm to .01 cm of color wavelengths. That span has more potential for color names than most people have imagination.
Our language and perception restrict the rainbow to seven colors, not the science of color wavelengths.
Colors Of The Rainbow And Beyond – FAQ
Rainbows are full of trivia beyond debating if poor indigo should remain as one of the visible colors. So here are a few other FAQs we’ve gathered for you.
Are Rainbows Different Shapes?
The arch of a rainbow is often compared to a bridge. But the truth is rainbows are always a full circle. We only see part of it due to standing on the ground.
Is A Fire Rainbow A Real Rainbow?
A Fire Rainbow is not a real rainbow or on fire. They are actually a Circumhorizontal Arc, which is created from ice halos.
Is A Moonbow A Real Rainbow?
Moonbows are real rainbows, unlike the Fire Rainbow. The sunlight is being reflected off the moon.
Is Pink A Color In The Rainbow?
Pink isn’t a color in the rainbow because it doesn’t have a wavelength.
Is Magenta A Color In The Rainbow?
Magenta is also not a color in the rainbow for the same reasons pink is excluded.
Are X-Rays A Color In The Rainbow?
X-rays are not typically included in the color spectrum, as their wavelengths come after ultraviolet. However, X-Ray Rainbows are a thing and can help scientists calculate distances in space.
How Many Colors Did Aristotle See In A Rainbow?
Aristotle postulated that all colors came from white and black. His different perspective on color had him seeing only three in a rainbow: red, green, and violet.
Do Other Planets Have Rainbows?
Scientists believe it is highly likely that Titan, one of Saturn’s moons, has rainbows.
The seven colors we perceive in a rainbow are shaped by our language and Sir Isaac Newton’s admiration of Pythagoras.
However, while we can debate what to call color, the wavelength is measurable. Thus, even if indigo gets kicked out of rainbows, the wavelengths will remain in the same order.
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