I love the color blue! It’s not found as often naturally as I’d like. Someone’s probably written a doctoral thesis on the topic, but it seems that evolution favors other colors.
Cones, the color receptors in our retinas, are most sensitive in the green range. In fact, much on our planet skews towards green. Plants are chock full of chlorophyll, which gives them a green hue. Chlorophyll is found on every single plant on Earth. Look outside in spring and summer for clear evidence of this.
Okay, you’ll say what about the sky? The sky is blue but that isn’t a pigment. That is due to a phenomenon called Rayleigh Scattering. (The scattering of sunlight off the molecules in our atmosphere. This is more effective at shorter wavelengths. That makes sense because blue is on the shorter end of the visible light spectrum.)
Scattering is also why blue jays are blue. (The birds, not the team) Blue jays produce melanin, meaning the birds should technically appear almost black. However, tiny air sacs in the bird’s feathers scatter light, making it appear blue to our eyes.
Now you’ll say, but what about the oceans? They’re blue!
It turns out that water is not blue because of reflected skylight. This is a common misconception!
According to NOAA, (National Oceanic and Atmospheric Administration) the ocean is blue because of the way it absorbs sunlight.
Water strongly absorbs long-wavelength colors at the red end of the visible light spectrum. It also absorbs short wavelength light, including violet and UV.
Water can take on other hues–including red and green– if light bounces off
nearby objects, such as algae near the surface.
So, let’s get back to pigments. Perhaps people find blue valuable because it is uncommon. The economics of supply and demand in action?
100,000 years ago, humans used red and yellow ochre from clay, as well as charcoal to create pigments. To incorporate blue into their lives, Babylonians and Egyptians used bits of lapis lazuli, a blue semiprecious stone.
Lapus Lazuli (above)
In the sixth century, evidence from Turkish burial sites suggests that humans ground minerals down to a fine powder. This wasn’t easy.
The main reason why blue is so elusive has to do with the relatively narrow range of pigments found on our planet that create coloration. Red and orange pigments are produced by carotenoids, brown and black pigments are produced by eumelanins and yellow pigments are produced by pteridine compounds.
Plants have an easier time producing blue pigments thanks to anthocyanins. And I spend my summers adding fertilizers so my hydrangeas stay blue! (No, these are not MY hydrangeas….I wish!)
These are mine though….more purple than blue. Blue is tough!
Sapphires are actually formed from the mineral corundum, which is clear. When trace amounts of iron or titanium come in contact with the corundum as the crystals form, they are incorporated into the structure. (No, this is not my necklace either…I wish!)
However, most creatures in the animal kingdom are unable to make blue pigments. Any instances of blue coloration you come across in animals are typically the result of structural effects, such as iridescence and selective reflection.
Science aside, I am wondering….
Do you have a quest for blue? What is your favorite color?
Louie isn’t blue, but I don’t hold that against him! Don’ t miss out on more posts so we can make sense of science together. Be sure to subscribe!