Why are plants green? The answer to this is some pretty basic physics.
The colors of light that we receive from the Sun have different energies. Red is the lowest of these energies followed by yellow, green, and blue. The sunlight with the highest energy that actually reaches the surface of the Earth is green. Blue light, which is more energetic, is refracted away by Earth’s atmosphere and scattered as it interacts with molecules in our upper atmosphere. That’s why the sky is blue.
When you look at an object, the color you see is the color reflected by that object. A red ball is red because it reflects red and absorbs all other colors. A green leaf is green because it reflects green and absorbs all other colors. If the highest energy of light reaching the surface of the Earth is green, and if the leaf reflects green, what does this do for the leaf? The answer should be pretty obvious – it keeps the leaf from absorbing too much energy and getting cooked. In the fall of the year when the leaves lose their chlorophyll A, which gives them the green color, what happens? The leaf gets cooked, falls off the tree, and we have to scrape it off the yard.
If a planet had a different atmosphere so that a different energy of light reached its surface, its plants would have to be a different color. To quote Kermit the Frog “It’s not easy being green.” Why are plants green? They are green because green is essential to life on Earth.
This explanation is greatly oversimplified. Obviously, not all plants have green leaves. Some plants live under a canopy of other trees and have to use a different system. The design of life on Earth is incredible, and the green trees and grass around us testify to the wisdom of God in making a place for life to exist.
We have a children’s book titled Why Is the Sky Blue, Why Is the Grass Green. You can read it and all of our children’s books on our Grandpa John’s Science Club site using THIS LINK.
–John N. Clayton © 2018