Part 3: Blue Feathers

Here is part 3 of my 4 part series on the scattered blues. Check out part 1 here and part 2 here.

Blue feathers have evolved in many species of birds. A blue jay's plumage is an excellent example with blue and white. You can see the black and blue of a Steller's jay in your own backyard. A male mountain bluebird has blue plumage of this type along with the head feathers of the male lazuli bunting; both can be found in central British Columbia. We know that feathers don't contain blue pigment, so the colour must be a result of the feather's structure.

In the late 1800s, just after the discovery of Rayleigh scattering, naturalists used this new concept to explain why blue feathers were blue. Since they didn't have the tools to examine the nanostructure (structure in the order of a billionth of a meter) of a feather, naturalists assumed that within the feather there existed transparent cells full of particles that were tiny enough to create Rayleigh scattering. Like the sky, blue light would be more efficiently scattered. These transparent cells would also contain pigments to absorb the longer wavelength colours. As a result, to our eyes these birds would appear blue.

Because Rayleigh scattering is incoherent, it produces the exact same colour irregardless of the observation direction. Since blue feathers in natural light don't change colour depending on what direction the naturalists looked at them, the assumption that their colour was formed through Rayleigh scattering seemed valid. But, in the 1930's, scientists examined a a non-iridescent blue feather under a directional light source. Colour variations were observed as the light source was moved – an iridescent characteristic that called into question the hypothesis of Rayleigh scattering making the feather blue.

By the 1940's, a cool new gadget came on the market – the electron microscope. Now naturalists could directly examine the internal nanostructure of blue feathers. Based on this first look, they interpreted the internal feather structure to contain randomly spaced objects. This meant scattered light would be incoherent leading giving support to the hypothesis of Rayleigh scattering. It took decades of further research to change this hypothesis and in the mean time many textbooks were written explaining that blue feathers were the result of Rayleigh scattering. By the 70's, scientists finally determined that the nanostructures were, in fact, not fully random. Instead they were a quasi-ordered matrix – not quite the perfect order of iridescence but not the full randomness required for Rayleigh scattering. Under natural light from all directions, like sunlight, these feathers appear to be the same colour from all directions. However when a directional light is shone on blue feathers the colour will change depending on the light direction.

Since the colour of a Steller's jay's feather comes from its internal structure on a tiny scale, a damaged feather would lose its blue colour. The dark pigments in the feather, that act to help show off the blue, would make damaged feather would look almost black. So if you are lucky enough to find a Steller's jay feather, take care of it.

Thanks to G. Hanke for the photo of mountain blue birds.

Part 2: Blue Skies

Here is part 2 of my 4 part series on the scattered blues. Check out part 1 here.

On a sunny day, we perceive blue blanketing the sky, but, in reality, the sky has no colour. When traveling towards us, sunlight first hits earth's atmosphere. Earth's atmosphere is primarily composed of nitrogen (78%) and oxygen (21%) with bits of dust, water vapour and some inert argon, among other things. Water vapour and dust are the physically biggest components of the atmosphere, and are relatively large compared to the wavelengths of light. When light hits the water vapour and dust, is reflected in different directions, but the light remains white. So why does the sky appear blue?

In 1810, Goethe gave this explanation: “If the darkness of infinite space is seen through atmospheric vapours illuminated by the daylight, the blue colour appears.” His theory said colour comes from something within the atmosphere during the light of day. About the same time a more scientific inquiry was being made into the nature of scattering light. John Tyndall showed in an 1869 lab experiment that the blue hues of the sky could be created when white light was scattered by tiny particles. A few years later in 1871, John William Strutt, also known as Lord Rayleigh, was the first to describe the actual mechanism that makes the sky appear blue was a result of the tiny gas molecules of the atmosphere instead of the larger dust and water vapour.

When light collides with a gas molecule the results are different than when light hits a relatively large dust particle. Gas molecules are tiny compared to the wavelengths of light – several thousand times smaller. When light strikes a molecule, that molecule absorbs a specific wavelength (or colour) of the light's energy and later re-emits the same colour in all directions; a process called Rayleigh scattering. This type of scattering is an example of incoherent scattering. Lord Rayleigh discovered that molecules absorb energetic light (blues) at a much greater rate than less energetic light (reds).

Most of the longer wavelengths of light pass through our atmosphere unaffected, resulting in the full spectrum of sunlight with a higher ratio of blue wavelengths from the scattering. For this extra blue light to make the sky appear a brilliant blue, a dark background is required. Fortunately, beyond our atmosphere is the blackness of outer space, which makes an ideal dark background. The combined effect of the extra blue light and the black of outer space results in a sky that appears blue.

If you shift your gaze towards the horizon, the brilliant blues give way to paler colours and perhaps even white. The light reaching you from near the horizon passes through much more atmosphere, so the scattered blue light is scattered again and again, reducing its intensity. This is another consequence of Rayleigh scattering. Preferential scattering of blue light by our atmosphere occurs everywhere, not just above us. For example, light reflected from your hand to your eye is affected by this scattering, but the effect is so minuscule we can't detect it. Over a longer distance, like to a range of distant mountains, there is enough atmosphere to superimpose a blueish haze on our view of the mountains.

Part 1: Blue Skys and Blue Feathers – The Scattered Blues

A while back I wrote about why the sky was blue and why some feathers are blue (here) – well I didn't quite get it right, so I'm trying again. I've written a more detailed explanation which I'll post in four parts.

When I look around, I see lush greens of temperate rain forest, rich browns of fertile soil, lively yellows in fluttering butterflies, and luscious reds in ripe berries – but, not a lot of blues. If the sky is clear, it's the biggest blue object around, extending from horizon to horizon. Water reflects the blue of the sky, adding another layer of blue. On a lucky day, I'll catch a glimpse of a Steller's Jay showing off it's blue and black plumage, or a shimmering silver-blue dragon fly will dart by. I might even see a rare blue flower. On a gray winter day, the blue eyes of my favorite companion may be the only brilliant blue around. Other natural places have their own blue components, but in general, blues aren't common in nature. In fact, world-wide there just isn't a lot of natural blue pigments, thus the blues we see are often the result of optical properties within an object. These colours created as the result of an object's structure are called, creatively, 'structural colours'. Blue is a very common structural colour, and to understand why we'll need to start with some optics.

Sunlight is called 'white light' because it appears colourless. Within this colourless light lurks the full colour spectrum. Once, people thought white was the fundamental colour of light, and colours formed when something was added into the light. This theory was changed after the careful experimentation and observations of Sir Isaac Newton. Around 1670, Newton shone light through a prism creating a rainbow of hues on the other side. From this result, he concluded that white light contains all colours and that the prism simply separates them. Therefore, colour results from interactions between an object and light.

We now understand that white light is made up of tiny waves (which are simultaneously tiny particles if you want to add complexity). Light waves travel at the same speed but can have different wavelengths, that is, the distance between successive crests. Our brains perceive the different wavelengths as different colours. The longer wavelengths form reds, oranges and yellows, and the shorter wavelengths form greens, blues and violets. If you could watch waves of light pass by, more waves of blue would pass compared to waves of red – this means that the blue light has more energy. Light travels outward from its source, the sun, in a straight line until it collides with something. This collision could release all the hues in the spectrum or just a select few.

Scattering describes how light is diverted from its original straight path. Light scatters in two ways: coherent and incoherent. When scattering is coherent, spectacular effects such as iridescence can occur. Like a ball bouncing back from a flat wall, the light reflects precisely because the reflecting surface is geometrically regular. Similar colour light waves augment each other, further intensifying the effect. An iridescent feather's colour can change depending on viewing angle, a phenomenon easily observed in a Anna's Hummingbird gorget. Incoherent scattering resembles the result of throwing a rubber ball at a pole – it could bounce away in any direction. In this case, the scattering objects are randomly distributed relatively far apart. Scattering at one object occurs completely independently of the scattering at the other objects. Both coherent and incoherent scattering occur regularly in nature and can provide the mechanism for creating blue colours.

The photo is of a hyacinth macaw I took years ago at the San Diego Zoo.

Chaos

Back in the mid 90's, when I was on a winter army exercise, I was lent a copy of James Gleick's Chaos. We were in the middle of Alberta and it was cold – so cold we had moved our accommodations out of tents and into a heated H-hut (H-huts were built as temporary army barracks during WWII that were still in use). Our exercise was shut down until the temperature increased, so I had plenty of time to read.

I have always read about math and science. On one command post exercise, the brigade commander caught me reading during a lull in the action. In jest, he made a big deal of it. I suspect he thought I was reading a trashy romance novel, but instead I was reading a book on math. Shocked to discover the topic of my reading material, he told me that if math was what I was reading about then I was welcome to read on any of his exercises.

The book Chaos was the first time I had heard of chaos theory. I loved it. The fact that seemingly simple processes could generate such complexity was fascinating. Now I saw dripping faucets and swinging pendulums as gateways to observing chaos. To me, the most fascinating chaotic idea was turbulence. Water is complex! Move it just a bit and all sorts of phenomenon spring up including eddies and whorls.

Chaotic turbulent motions are found within the surface of stars, in combustion, in the ocean - even in water flowing from a faucet. Leonardo da Vinci included turbulence in his extensive studies, and he probably wasn't the first to study it. In all the centuries turbulence has been studied, we still haven't come up with a precise definition of what turbulence is. We know turbulence is what takes over when smooth fluid motion breaks into a complex network of eddy-like structures at all scales. Da Vinci's sketches of tiny eddies within small eddies within larger eddies and so on demonstrates the different size scales through which turbulent flow breaks up.

In Chaos, James Gleick describes turbulence this way: 'It is a mess of disorder at all scales, small eddies within large ones. It is unstable. It is highly dissipative, meaning that turbulence drains energy and creates drag. It is motion turned random.'

Okay, a picture of waves breaking on a beach isn't exactly a picture of turbulence, but it is the best I have.

It's snowing

It's snowing like mad out and very windy. In my backyard, the periodic wind gusts whip up the snowflakes into whirls and eddies producing momentary white outs. Fortunately, I don't have to go anywhere today. It doesn't snow often where I live, usually it remains green throughout the year. When it does snow it's like magic to me, the landscape is transformed from green to white like a idyllic Christmas card. The world seems hushed and new.

Today, the snow flakes are medium in size – not like our usual massive wet flakes that vanish once they hit the ground, or like the tiny prairie snowflakes that can be swept away with a broom. Each snowflake is a wonder of sharp-edged geometry. I don't know if each snowflake is truly unique or not – but I accept that it could be true. What I do know is that snow is just water and knowing this doesn't take away from the magic of a snow storm (if I'm inside).

Snow is just water – school children know this (hopefully, they also know about the perils of yellow snow). Winter outdoor survival manuals warn against eating snow directly only because it is cold – they just want you to melt it first.

I found a paper from 1673 on 'some observations touching the nature of snow' by N. Grew in the Philosophical Transactions of the Royal Society of London. He questions how snowflakes form and their geometry. He deduces that snowflakes come from icicles that form inside snow clouds. As they descend they thaw a bit, bump together and break apart eventually becoming the snowflakes we know.

For our modern view of how snowflakes form check out this.

An essay on turbulence

An essay of mine on one of my favorite topics (that is turbulence) has been published in my university grad journal. Check it out here.

A bloody green

Further to my post from yesterday, I stumbled across an interesting article from the 1818 edition of the Philosophical Transactions of the Royal Society of London, volume 108, pages 110 to 117. The paper was called 'A Few Facts Relative to the Colouring Matters of Some Vegetation' by James Smithson – an interesting person that I'm planning on digging up more information on.

I found this buried at the end in a section called 'Some Animal Greens':

There are small gnats of a green colour: crushed on paper, they make a green stain, which is permanent.

This brings to mind a child squishing bugs to see what colour their insides are. I've found no other reference to green dyes from gnats, so I'm assuming crushing gnats didn't make it into commercial production.

Actual bloody colours

I've been thinking about my bloody colours post of a little while back. Magenta and solferno were named because they reminded observers of the after effects of a battle. What about colours made from actual blood? That is, by killing a critter. These dyes exist, and some are still in use today.

Fantastic reds can be made from crushed insects. I wonder who was the first who thought of grinding up dried bugs to dye cloth? One of these dyes is Kermes, an ancient dye extracted from an insect (Coccus ilicis) that resided in the middle east. This bug lives as a parasite on oaks, producing carminic acid (the base component for a dye) to deter predators. Kermes is the root of the word crimson and predictably, cloth dyed with kermes turns out a bluish-red. Skilled dyers could even produce a scarlet cloth. About 70,000 insects are needed to make only one pound of dye – making a very bloody dye.

Cochineal, also known as carmine, is another ancient bloody dye produced from similar insect (Dactylopius coccus). This bug resides on cactus in Mexico and has been the foundation of a red dye for millennium. This dye is chemically the same as kermes except ten times stronger – less of them needed to die to produce the same amount of dye. When the Spanish brought this dye back to Europe in the mid 1500s, it quickly over shadowed kermes because it was a cheaper alternative. Both kermes and cochineal have been widely used to colour foods dating back to the middle ages, and cochineal is still in use now. As a food colourant it's called by many names, including 'natural red 4'.

Throughout the ages other similar insects have been used to make red dyes. Polish cochineal (Porphyrophora polonica), a insect that lives on the roots of herbs in Poland, was once used to make reds as an alternative to kermes. In India, a red dye was made from a secretion left behind by an insect in the same family (Laccifer lacca), I think the bug got to live in this case – but, I don't know for sure. In South East Asia, reds called lac, could be made from a whole family of related insects, which also provided the foundation for shellac (often used as a protective coat for wood).

Tyrian purple held the title of the most prestigious dye in antiquity. In Roman times if you were caught wearing clothing dyed this purple and weren't royalty it was considered a crime, of course affording this colour if you weren't royalty was virtually impossible. The complex technique for making this dye was discovered around 1500BC by the Phoenicians, an ancient Mediterranean seafaring traders. Tyrian purple is made from a pale yellow mucous secretion from some molluscs, commonly known as sea snails. It is possible to 'milk' these snails, in which case, they wouldn't be harmed – however, this is labour intensive so more destructive methods were used. Often the snails would simply be crushed to get their secretion. From one source, the snails were salted and left for three days to extract the liquid. The liquid was boiled for ten days after which fibers would be soaked in the resulting liquid for five hours. Finally, the resulting fabric would have to be exposed to sunlight where it changed colour from deep yellow, through green and blue to finally purple.

To dye a metre of cloth, 12,000 molluscs would be required (ie killed). Since they were making luxury fabrics, often a fabric would be dyed more than once to get the best shade. Different snails gave different shades, to get the best purple cloth would be first dyed in one species of snails then in another. Fortunately for the snails, synthetic dyes have completely replaced the original tyrian purple.

For more info check here, including some nice pictures.

A recycled documentary idea

Every couple of years, when I'm channel surfing, I stumble across a new documentary on what happened to the Amber Room. By the way, it's still lost. The Amber Room was built for a palace near St. Petersburg of gold leaf, mirrors and amber. The shiny yellows and golds are ornately detailed for an aristocratic taste found in another era. The room's complex construction took about eight years from 1701 to 1709 and included six tones of amber. In WWII, the room was covered in wallpaper in an attempt to prevent looting. It didn't work. The room was crated up by the Nazi's and shipped off. Although there has been repeated announcements of imminent discovery and theories on its fate, the Amber Room has yet to be recovered (it has however been reconstructed).

Along the Baltic Sea, pieces of amber wash ashore and have been collected since the stone age. The Dominion Republic is also a great place to find amber. In fact, amber is quite common and found all over the globe. But, what is amber? According to Wikipedia, it's fossilized tree resin. Coniferous trees are big producers of resins which is a hydrocarbon secretion. If you have ever handled a chunk of fir or pine tree, the turpentine like smell from the sticky residue left on your hands is the resin. Varnishes, adhesives, incense and perfumes have all been made from resins throughout the eons. Resin is different than sap, as sap is the fluid that transports nutrients around a plant (maple syrup is an example of a product made from sap).

Most amber is a warm yellow to orange brown. It's known to range in colour from a pale lemon yellow to red. Rare blue amber is formed when pyrites are included. Amber is often considered a gem stone, although it's not indestructible like a diamond.

To me, the most interesting thing about amber is that it can provide a window into ancient worlds. The oldest amber found so far is 320 million years old. We can learn about trees that have since gone extinct from the amber they produced. Since, resins are sticky stuff, the fossilized version ends up with all sorts of interesting things in it. Pollen from when our climate was different can be pulled out of amber giving us clues about ancient conditions.

The most spectacular are the trapped critters – insects, spiders, frogs and lizards. One misstep into the resin and these creatures are forever trapped. Baltic amber has few critters while Dominican Republic amber has more. Over the last few years scientists have isolated DNA from trapped termites, bees and butterflies. A great amber deposit with insects was recently found in India which promises more interesting finds. However, the Jurassic Park concept of isolating dinosaur DNA from the mosquito that bit it, is still fiction.

As a side note: amber ale has the deep yellow-orange of stereotypical amber, thus the name (no actual amber is involved in making amber ale).

More than iron

I tend to be low in iron and periodically have to take iron supplements. Right now I have the supplement my doctor recommended to me and I've made the mistake of looking at the ingredients. After the iron (which I'm okay with because it is the point of taking these) there is: D&C yellow no. 10, FD&C red no. 2, FD&C red no. 3, FD&C yellow no. 6, gelatin, lactose, povidone, silicon dioxide, sodium lauryl sulphate, sucrose, talc and titanium dioxide. All I wanted was some iron, instead I'm getting a hockey sock full of chemicals. I'm also confused why my iron pills have to be a bright red.

D&C yellow no. 10 (quinoline yellow) is derived from petroleum or coal tar. It has regulated minimums of lead, arsenic, mercury and cadmium, which scares me a bit. FD&C red no. 2 (amaranth) is another coal tar derived dye that is actually banned in the the United States because it is a carcinogen. FD&C red no. 3 (erythrosine) is the same dye dentists use to demonstrate how much plaque are on your teeth. FD&C yellow no. 6 is a lemon yellow dye that may cause everything from hives to kidney tumors.

More adverse reactions of inactive ingredients can be found here.

The gelatin is likely needed to make the outer capsule – so I'm okay with that. Lactose is a sugar found in milk, plenty of people can't tolerate it, so why include it? Povidone is a binder which is also used in glue sticks, I don't know if it is bad or not. Silicon dioxide is probably harmless. Sodium lauryl sulphate is highly effective in getting oil stains out. Sucrose, also known as table sugar, isn't too bad. Talc is added as a glidant, which I assume is to help the pill go down or make the manufacturing process smoother. Titanium dioxide is a white pigment that has also been used on rockets and as a sunscreen.

These 'non-medicinal' items may not be dangerous in the amount the pills contain, but I just don't think I need them. I'm going to find an iron supplement without all these questionable ingredients.