Health

Did You Know That Even The Bluest Eyes Are Technically Brown? Here’s Why

We know what you're thinking: Is this "the dress" all over again?

What color eyes do you have? If you answered blue, green or hazel, you’re wrong. You actually have brown eyes—everyone does. How can this be? Well let me ask you another question. Do you know why the sky is blue? Well, it turns out the same explanation tells us both why the sky appears blue and why every human technically has brown eyes even though they may appear blue or green.

Let me explain.

It all has to do with melanin. Melanin is a pigment that determines the color of our hair, skin and eyes. It consists of many tiny cells called melanocytes, and the ones in your eyes are located inside your irises.

“Everyone has melanin in the iris of their eye, and the amount that they have determines their eye color,” Dr. Gary Heiting, senior editor of All About Vision and licensed optometrist, told CNN.

There’s only one real “shade” of melanin, according to Dr. Heiting.

And it’s not blue or pink or yellow— it’s brown.

If your eyes are brown, you have more melanin in your irises; if they’re blue, you don’t have much. And if your eyes are green or hazel, you have an average amount of melanin in your irises—enough for your eyes to be partially brown.

But that’s not all. Have you noticed how some people’s eyes change color throughout the day? It all depends on the lighting and how light hits their eyes. Melanin absorbs light, which is why those with a lot of melanin have darker eyes.

When the light hits blue-eyed people, the light is reflected out of their eyes. This is called the Rayleigh scattering effect, as the light reflects back at shorter wavelengths.

Here’s a quick review of the visible light spectrum: Color is determined by the length of its wavelength. The shorter the wavelength, the more blue the human eye sees.

Humanly Visible Spectrum

There is some evidence that all blue-eyed people came from one ancestor, but it is not possible to predict eye color based on the color of a child’s parents’ and grandparents’ eyes. There are as many as 16 factors that have to align for your children to keep their blue eyes. Also, if you were wondering why all babies are born with blue eyes, it’s because melanin increases gradually during infancy. “As a baby develops, more melanin accumulates in the iris,” Dr. Heiting said.

Bonus fun fact: This scattering effect also explains why the sky is blue. Think of a sunbeam as a white light hitting the atmosphere, which contains all the colors of the rainbow (red, orange, yellow, green, blue, indigo and violet). The sun’s rays hit the tiny oxygen and nitrogen molecules (NOT water particles), and the blue and violet rays from the sun reflect back into the sky. The other colors come down to earth, which is why we see the sun’s rays as yellow and red.

And technically, the sky should be violet, since that is the shortest wavelength on the visual spectrum. But our eyes are more sensitive to the middle of the spectrum, so we see a blue sky instead of a purple sky.

If the sky was purple, we would see Purple Rain all the time with our brownish eyes.