It’s the color of the Emerald Isle, the hue of sickness and envy, and a shade associated with grotesque monsters. And its most universal interpretation conjures imagery of nature, a vibrant symbol of the environmental movement and healthy living.
Green, the mixture of blue and yellow, can be seen everywhere and in countless shades. In fact, the human eye sees green better than any color in the spectrum.
This, along with many other facts about this earthly color, makes it an essential part of our everyday lives.
But why is that?
Helping you see
We see green with ease because of how light reaches our eyes; the human eye translates waves of light into color.
When we see a green frog, the color that we see is the light reflected off of the surface of the frog’s skin, perceived by our eyes as green.
When we see these colors, the cones in our eyes are able to process the wavelengths and tell the brain what color is being observed.
Humans are trichromats, meaning we perceive three primary colors: blue, green and red. The retina in a human eye can detect light between wavelengths of 400 and 700 nanometers, a range known as the visible spectrum.
Each primary color corresponds to a different wavelength, starting with blue at the lowest (400 nanometers) and red at the highest (700 nanometers).
In the middle of the spectrum resides the color green, at around 555 nanometers. This wavelength is where our perception is at its best. Because of its position in the center of the spectrum, both blue and red light waves are enhanced and better perceived with the help of green waves.
Knowing your environment
Green space sweeps the planet. Before skyscrapers and suburbs popped up, our ancestors resided in forested regions full of greenery.
As they scavenged for food, the ability to differentiate between colored berries against the backdrop of green foliage was critical for survival.
The evolution of eyesight and the increasing ability to detect color with fine detail gave our primate ancestors an evolutionary advantage over other mammals who could not discern such differences as well.
Color changes in leaves, fruits and vegetables can indicate age or ripeness and even offer a warning that something may be poisonous or rotten.
Today, we continue to use this ancestral instinct at a farmers market or grocery store.
Sourcing your food
Bananas, though widely considered to be a yellow fruit, start off as green due to the presence of chlorophyl. Just as grass and leaves have chlorophyll to give them color, so do fruits.
Located in the cells of plants, chlorophyl plays a crucial role in photosynthesis, allowing plants to harvest energy from sunlight and convert it into energy that the plant can use to grow.
The molecule absorbs blue and red light well while reflecting the green light that we see.
The peels of bananas are bright green in color until the chlorophyll inside the peel begins to break down. As the fruit ripens, the molecule in the peel breaks down and we observe a color change from green to bright yellow—and we prefer to eat yellow bananas because they are sweeter.
While the chlorophyll in the banana breaks down, the starch in the peel is converted into sugar, so more yellow means more sugar—until it begins to rot.
Because of their high starch content, greener bananas are sometimes favored as a cure for upset stomachs.
This change in color also applies when glancing over an aisle of bright bell peppers. Our eyes help us find our favored ripeness and sweetness. Green peppers, with more chlorophyll, are less sweet. As they turn yellow and red, the peppers become sweeter.
When we’re enjoying a salad, a brown piece of wilted lettuce or kale is almost always discarded. And our eyes tell us the lawn is overdue for some maintenance when the color darkens.
So although we may not reside in the forests anymore, our keen perception of green continues to play a significant role in keeping us healthy.
Keeping you calm
Some scientists and researchers also believe that because our eyes are at the peak of their perception to detect the wavelengths corresponding with the color green, the shade may calm us down.
With less strain to perceive the colors, our nervous system can relax when perceiving the tone.
This sedative quality of green may explain why there is so much of it in hospitals, schools and work environments. Historically, actors and actresses would recess to green rooms after so much time looking into bright lights on stage, though modern “green rooms” are rarely painted green.
Helping you live longer
Natural environments, full of green vegetation, might help you live longer.
A 2016 study found that living in or near green areas was linked with longer life expectancy and improved mental health in female participants. Researchers from Harvard T.H. Chan School of Public Health and Brigham and Women’s Hospital compared risk of death with the amount of plant life and vegetation near the homes of more than 100,000 women.
After the eight-year study was completed, the data revealed that participants who lived in the greenest areas had a 12% lower death rate than women living in the least green areas.
With more green space, study authors said, came more opportunity to socialize outdoors. Additionally, the natural settings—compared with residential regions where plants and greenery were sparse—proved to be beneficial to mental health.
“We were surprised at the magnitude of the mental health pathway,” said Peter James, study author and research associate at the Harvard Chan School’s Department of Epidemiology.
Of those who did not live in greener areas, respiratory issues were the second highest cause of death. The study indicated that less exposure to polluted air may have been one of several reasons for increased life expectancy among for those who lived in green areas.
Our ancestors lived their entire lives outdoors. The benefits we stand to gain from adopting an outdoor mindset, James says, could have a positive impact. “We know already that vegetation can help mitigate the effect of climate change. Our study suggests the potential co-benefit for health.”
Written by Robert Jimison for CNN
CNN Animation by J. R. Canedo and Rafael Mayani
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