Have you ever wondered why there are no green mammals?
After all, for those who spend long periods of time hiding in vegetation, being able to camouflage themselves into their surroundings is very convenient.
One reason is that green is hard.
Plants use chlorophyll to do this, but there are actually no other green pigments found in nature.
So how do parrots and frogs do it?
Well, they overcame the shortage of green pigment by using a richer yellow pigment.
With this, you just need to mix it with blue, But here’s the thing.
In fact, much of the difficulty in obtaining the color green lies in the lack of the ubiquitous color of the sky and sea.
There is no true blue color or pigment in nature, so both plants and animals have to perform tricks to appear blue.
One of the tricks is Structural coloringIt’s an amazing phenomenon that occurs when light interacts with the microstructure of a surface, showing us color despite the absence of pigments.
In parrots and frogs, these microscopic structures in feathers and skin allow only blue light to be reflected, and when combined with yellow pigments, Make them look green.
Did you notice we said “seems”?
we must never forget “Color is a perception, not a physical property of light”As noted by David A. Mackey, a distinguished professor at NHMRC in Australia.
“That’s why I ask my students: ‘What color was the Big Bang?'” he writes in Eye, the scientific journal of the Royal College of Ophthalmologists.
“Because no one was present to perceive it, there was no color; in fact, visible light did not appear until 380,000 years later.”
Visible light is the sun’s white light and is a mixture of many colors, each with a different frequency.
Our eyes can only perceive three colors: red, green and blue, but by combining them we can perceive many more. What we perceive is what is reflected after taking in all other factors.
Now, in the biological world, the vast majority of colors are produced by pigments, compounds produced by living organisms that selectively absorb certain wavelengths of light.
But in the absence of pigments, the magic of structural coloration occurs, and this change in light often gives us The most dazzling color.
And it is also the most durable becauseUnlike the colors produced by pigmentation, which degrades when the organism dies, the microstructure remains until it breaks down.
Let’s deconstruct it
To better understand structural coloring, let’s stick with blue, This color is difficult to obtain in nature.
The reason it still occurs is that blue light has a very short wavelength, so it is reflected more easily than other colors with longer wavelengths.
This was first recognized by scientist John Tyndall in 1869, when he observed that tiny particles in the atmosphere preferentially scatter blue light, creating the familiar blue skies on clear summer days.
Soon after, Lord Raleigh (John William Strutt) demonstrated that the particles Tyndall spoke of were actually individual gas molecules, specifically nitrogen and oxygen.
The same thing happens with the feathers of birds like the hyacinth macaw.
If you were to look at a feather under a high-power microscope You will see that the surface layer of keratin has a milky white color due to the presence of small pores.
These tiny pores act like tiny particles in the atmosphere, and the dark melanin particles absorb longer wavelengths of light, enhancing the blue color.
For comparison, if you look at a red feather under the same microscope, you’ll see that the surface is transparent, but the underlying structure is filled with red pigment particles.
Similar but not identical physical phenomena produce rainbow colorsLike the thin film of oil you see on water or on a hummingbird feather, its microstructure reflects sunlight through a natural form of nanotechnology.
the brightest one
British scientists Robert Hooke and Isaac Newton first observed this type of structural coloration in peacocks; a century later, polymath Thomas Young explained his principle and called it wave interference.
Young described iridescence as the result of interference between reflections from various film surfaces and the refraction of light as it enters and leaves such films.
The geometry then determines that at certain angles, the reflected light appears different colors at different angles.
A typical example is the fruit of the African plant Pollia condensata, The brightest living substance in the world.
This was confirmed by a team of researchers from Kew Botanic Gardens in London, the University of Cambridge in the UK and the Smithsonian Museum of Natural History in the US.
They were initially interested in an unusual property: small metallic fruits called marble berries that retain their vivid blue color years or even decades after being picked.
While examining the berries, they realized that beneath its smooth, specular surface were multiple layers of specialized cells made of cellulose fibers, each of which rotated slightly.
When light reaches the upper layer, some of it is reflected and the rest is filtered by the rest.
The light reflected from each layer is unusually bright and produces intense colors, an effect called Bragg reflection.
The scientists determined that the fruit tissue was more intensely colored than any biological tissue previously studied.
Even more intense than the famous color of the wings of the blue morpho butterfly native to Central and South America. Although not as bright as the marble berry, it is a star in the world of structural coloration because it is more than just an example. It is the inspiration for technology.