You may have learned that leaves are green because they're full of a green molecule called chlorophyll — it's the reason for the greenness of plants, from moss-green moss to grass-green grass to ever-green evergreens.
And the reason chlorophyll is so incredibly popular — showing up in nearly every plant on Earth is that it's good at soaking up sunlight.
The more light a plant gets, the more energy it has to make sugar and grow tulips and kumquats and do all the other things plants do.
But wait a second: doesn't the fact that chlorophyll is green mean that it's actually bad at absorbing green light?
I mean, sunlight is composed of the whole rainbow of colors, each a separate wavelength, and the colors we see when we look at a leaf are the wavelengths that leaf isn't absorbing — that is, they are the ones that bounce off the leaf and reach our eyes.
Chlorophyll is great at absorbing reds and blues, but if it were really awesome, wouldn't it absorb all colors of light, green included, giving us a world full of black moss and black grass and ever-black trees?
So why aren't leaves black?
And since they apparently don't have to be black, what's stopping them from being red or blue instead?
Is green just Nature's favorite color, or is there something special about those wavelengths of light?
The short answer is that we don't know for sure.
