Purple:
A Color Made by Your Brain
To understand purple, what do we need to understand first?
Light is a wave. What do we call the distance between two wave crests (or troughs)?
Your eye sees one piece out of how many pieces of light? (Bonus: What fraction is this?)
Give an example of a long wave.
Give an example of a short wave.
List the colors of a rainbow (or prism) in order.
Why are violet and purple not the same color?
What do we call the special cells in your eyes that allow the brain to see color?
Do your best to explain how your brain “creates” purple.
Purple is a “nonspectral” color. List three or more other nonspectral colors.
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Purple:
A Color Made by Your Brain
What Makes Purple Special?
Purple is different from every other color you see.
When you look at a purple flower or a purple shirt, something amazing happens inside your brain. Your brain actually creates the color purple.
Purple doesn't really exist in the world around us the same way other colors do. It's like a magic trick that your brain performs every time you see something purple.
This might sound strange, but it's true.
Purple is your brain's creative solution to a problem. When your eyes send confusing information to your brain, your brain makes up purple to help make sense of what you're seeing. It's a beautiful example of how smart and creative your brain really is.
How Light Works
To understand purple, we need to learn about light first.
Light is energy that travels in waves from the sun to Earth. Think of light waves like ocean waves, but much smaller. Scientists measure these waves by looking at the distance between one wave and the next. This distance is called a wavelength.
There are many different types of light waves.
Some are very long, like radio waves that carry music to your radio.
Others are very short, like the waves that make your microwave oven work.
All of these different types of light waves together make up something called the electromagnetic spectrum.
Your eyes can only see a tiny part of all the light that exists. In fact, you can only see about one tiny piece out of every 3,000 pieces of light that surrounds you.
The light you can see is called visible light. It includes all the colors you know, from red to violet.
The Rainbow of Colors
You've probably seen a rainbow after a rainstorm.
The colors in a rainbow always appear in the same order: red, orange, yellow, green, blue, indigo, and violet. Some people remember this order by using the name Roy G. Biv, which uses the first letter of each color.
In this rainbow, red light has the longest waves. Blue and violet light have the shortest waves. Green and yellow light have medium-length waves. Each color in the rainbow is made by light waves of a specific length.
Here's something important to remember: violet and purple are not the same color, even though they look similar.
Violet is a real color that appears in rainbows. Purple is something your brain creates.
How Your Eyes See Color
Your eyes are like amazing cameras that capture light.
On the back of each eye, you have special cells called cones. Most people have three types of cones, and each type is good at detecting different lengths of light waves.
Scientists sometimes call these cones red, green, and blue cones because each type works best with one of those colors.
But the cones don't actually see color. Instead, they detect different wavelengths of light and send messages to your brain.
The red cones are best at detecting long wavelengths of light.
The green cones work best with medium wavelengths.
The blue cones are best at detecting short wavelengths.
When light enters your eyes, it activates different combinations of these cones. Each combination sends a different message to your brain. Your brain reads these messages like a secret code and then decides what color you should see.
How Your Brain Creates Colors
Let's say you're looking at an orange.
The light from the orange activates your red cones and green cones, but not your blue cones. Your brain gets this message and says, "That's orange!"
If light activates mostly your blue cones, your brain decides you're seeing blue or violet.
Every color in the rainbow can be created by light of just one wavelength hitting your cones. This is why we can see all the colors in a rainbow or a prism.
Each color has its own special wavelength that creates its own special combination of cone activity.
The visible spectrum works like a straight line. Red is at one end, violet is at the other end, and all the other colors are arranged in between. As you move along this line, the activity in your cones gradually changes from one type to another.
The Purple Problem
Now we come to the mystery of purple.
Purple creates a big problem for your brain.
When you look at something purple, it activates both your red cones and your blue cones at the same time. This is very confusing for your brain.
Your brain thinks, "Wait a minute! If the red cones are active, this should be red or something close to red. If the blue cones are active, this should be blue or something close to blue. But red and blue are on opposite ends of the color line. How can something be close to both ends at the same time?"
This is impossible to solve using the straight line of colors.
So, your brain does something very clever. It bends the straight line of colors into a circle. Now red and blue are next to each other instead of being on opposite ends.
Your Brain's Creative Solution
When your brain bends the color line into a circle, it creates a color wheel.
Now red and blue are neighbors. But there's still a gap between them. Your brain fills this gap by creating purple and all the different shades of purple you can see.
This is why purple is so special.
All the other colors you see are made by light of just one wavelength. Purple is made by mixing light of two very different wavelengths: long red waves and short blue waves.
Scientists have special names for these different types of colors. Colors that are made by just one wavelength are called spectral colors. These are the colors you see in a rainbow.
Colors that are made by mixing two or more wavelengths are called nonspectral colors.
Purple is a nonspectral color.
Pink is a nonspectral color.
Brown is a nonspectral color.
All Colors Are Brain Creations
While purple is special because it doesn't exist in the spectrum, all colors are actually creations of your brain.
Your brain takes the messages from your eyes and turns them into the beautiful colors you see every day.
Scientists who study how we see colors think this is amazing. Colors help us understand so much about the world around us. The color of a banana tells us if it's ripe or not. The color of leaves tells us what season it is. The color of someone's skin can tell us if they're healthy or if they need help.
Colors start with something very simple: light waves of different lengths. But they end up creating something complex and beautiful that helps us understand our world. Every time you see purple, remember that your brain is working like an artist, creating something beautiful from confusing information.
Why This Matters
Understanding how purple works helps us learn about how amazing our brains are. Your brain is constantly working to make sense of the world around you. When it gets confusing information, it finds creative ways to solve problems.
The next time you see a purple flower, a purple crayon, or a purple shirt, you can remember that you're seeing your brain's creative solution to a puzzle. Purple shows us that our brains are not just processing information. They're also creating beauty and meaning from the world around us.
This is just one example of how your brain works every day to help you understand and enjoy the world. Your brain is truly amazing, and purple is just one way it shows off its incredible abilities.
Activates - turns on or makes something start working
Combination - a mixture of two or more things together
Electromagnetic - a type of energy that includes light, radio waves, and microwaves
Nonspectral - colors made by mixing different wavelengths of light
Prism - a clear glass or plastic shape that splits white light into rainbow colors
Spectrum - the range of all different types of light arranged in order
Spectral - colors made by just one wavelength of light
Ultraviolet - a type of light that can burn your skin but you can't see it
Visible - able to be seen
Wavelength - the distance between one light wave and the next
► COMPREHENSION QUESTIONS
— please answer with complete sentences
To understand purple, what do we need to understand first?
Light is a wave. What do we call the distance between two wave crests (or troughs)?
Your eye sees one piece out of how many pieces of light? (Bonus: What fraction is this?)
Give an example of a long wave.
Give an example of a short wave.
List the colors of a rainbow (or prism) in order.
Why are violet and purple not the same color?
What do we call the special cells in your eyes that allow the brain to see color?
Do your best to explain how your brain “creates” purple.
Purple is a “nonspectral” color. List three or more other nonspectral colors.
► From EITHER/OR ► BOTH/AND
► FROM Right/Wrong ► Creative Combination
THESIS — Argue the case that purple really is different from other colors, like the colors in the rainbow.
ANT-THESIS — Argue the case that while, yes, your brain “creates” purple (and pink and brow), it also “creates” all the other colors, so, really, purple (and pink and brown) is no different from other colors.
SYN-THESIS — How does seeing purple (and pink and brown) from both perspectives help us understand our brain and how we make sense of the world?
