His exalted name, “Light,” touches the darkness
and everywhere is filled with light.
The letters written from a brilliant world
are revealed to the hearts;
Then the Divine command,
“Read in the name of your Lord!”
descends and becomes our intentions.

We look around the Earth and believe that we start to sail into the dark upon reaching the depths of the skies, the land, and the oceans. But if we look with care, we may notice that the inhabitants of those places often inform us of the beauties they are created with.

The depths of the oceans, especially, are where what we see leave us amazed. From microscopic bacteria to giant squids, and from tiny lighted jellyfish to spiny skin, many creatures, from ascidians to some sharks and stingrays, turn on their lights, literally, illuminating the darkness of the deep sea. This biological light-producing process in the body of some animals is called bioluminescence. It is astounding that these creatures can emit biological light with no change in their body temperature. Normally, light is formed by emitting heat. This basic principle applies to some of the most common sources of light that we know of, such as campfires and electrical lightbulbs.

A mechanism that produces light without heat has been created in some insects living under the sea as well as those on land. The basis of biological light production is generally the oxidation of luciferin, i.e. its conversion to oxyluciferin. The enzyme necessary for this chemical reaction to occur is luciferase.

Most living creatures that can produce bioluminescence live in deep, dark areas of the world’s various seas and oceans. Some of the inhabitants of these depths emit strong blue (secondarily green) light at an average wavelength of 475 nm. An interesting note is that underwater life forms are often created with sensitivity to the wavelengths of blue-green lights mentioned above. In rare cases, there are also sea creatures that emit light in the yellow-red wavelength range.

Animals with the ability to emit light are also usually given excellent control mechanisms so that they can use their equipment as a weapon. They can turn their lights on and off in a flash and can utilize complex chemical and neurological mechanisms that provide functions such as adjusting the intensity, color, and direction of the light. Creatures that produce light underwater sometimes do not need to use the light in order to see where they are going. Instead, they tend to use these marvelous gifts in a variety of strategic ways. Some will try to attract the attention of their prey; others will attempt to ward off predators and aggressors; still others will use their lights to indicate that they are ready for reproduction. It is even possible for some creatures to utilize several of these functions at the same time.

Let us now examine some specific species and how they employ bioluminescence.

Light vomiting shrimp

One of the most interesting examples of bioluminescence in animals is the light-emitting deep-sea shrimp Acanthephyra purpurea. This shrimp will actually vomit light from its mouth as a last-ditch effort to deter predators. The intent is to disorient, confuse, and even temporarily blind other creatures, similar to the effect of a flashbang grenade, so that the shrimp can retreat into the dark. As a result of their research on the shrimps, marine biologist Edith Widder states that the chemical substances sprayed are not blue when they are in the body and that the blue light production occurs when the luciferin substance in the sprayed liquid comes into contact with the oxygen in water.

Loosejaw fish

There are at least 42 recorded families of bony fish that have bioluminescent properties. One of them is the Photostomias guernei, or the “loosejaw fish”. This fish has a remarkable organ that emits light on the sides of its eyes. These lights, which resemble the headlight lamps of our cars, are not constantly lit, in order to avoid waste. When hunting, the fish illuminates the way ahead with the light it produces, and it can turn these lights off when they are no longer needed. A wonderful feature of this organ is that, just like headlights, a highly reflective layer is created behind the main center of the light. The reason that the fish is able to turn the light off may be because its black velvety body is contrasted by the light color of the organ and would thus attract much unwanted attention.

Deep sea hatchetfish

Bioluminescent systems were also given to creatures in order to act as a means of camouflage. They work phenomenally for both hunting and survival in situations where blending in with the environment is paramount for catching prey or evading predators. In the depths of the underwater world, the silhouette of an animal bathing in light is an easily recognizable target. One of the best examples of this phenomenon is the deep-sea hatchetfish. The fish has been created with its eyes on top of its body and its mouth facing upwards, making it easier to hunt. It also emits bioluminescence from its abdomen to provide camouflage against more aggressive, larger fish that swim lower than itself. The color of the light emitted makes it difficult to recognize the fish from below as it perfectly matches the color intensity of the environment. In the meantime, if the sunlight that hits the sea is interrupted in any way, the fish will turn off its lights and the camouflage will continue.

Black dragonfish

Diversity in the light organs of the scaleless black dragonfish (Melanostomias bartonbeani)

This species of black dragonfish (Melanostomias bartonbeani) takes advantage of luminescence in a number of ways. An illuminated area next to the eyes is used to find prey and send signals to its mates. The black dragonfish’s chin also has an illuminated extension that dangles in the waves as bait for naive prey. In addition, a set of small organs of light arranged along its abdomen play a role in concealing its silhouette. Furthermore, light-emitting pocket-like structures surrounded by a gelatinous capsule embedded in the skin are used as alarm systems. The bioluminescent systems within this creature are immensely complex and beautiful, and when observed in detail reveal the dazzling splendor of the world that we live in.

Fish with 3 different types of illumination

The Northern Stoplight Loosejaw (Malacosteus niger) has three different types of light organs, the complex use of which cannot be possible without top engineering skills. The wide, drop-shaped, illuminated organ under its eyes emits a red light at a wavelength of 702 nm as if it knows the laws of optics under the sea. This red light is not visible to most deep-sea creatures, for it is quickly absorbed in water. Yet, with this red light this fish is able to have vision in a close proximity while remaining largely undetected. This is similar to infrared binoculars soldiers use for night vision without giving away their position. The loosejaw is thus a dangerous hunter that has an edge over its prey. There also exists a blue light-emitting oval section, behind the organ, that emits red light and is usually larger in males. A third light organ is round and smaller and is located between the eyes and the red-light organ.

Angler fish

The angler fish is one of the most iconic fish of the deep ocean due to its famous rod and bioluminescence. The angler fish does not actually produce its light on its own: the light is credited to bioluminescent symbiotic bacteria that inhabit the end of the rod on their forehead. This illuminated part, which resembles a worm-like bait, is very attractive to small fish. These fish are thus lured to the angler expecting a quick snack, but instead the angler swallows them whole with its massive mouth. While doing their task of helping the angler hunt small fish, the bacteria maintain a symbiotic relationship with the fish and also find an environment in which to proliferate. In this way, they form a good example of cooperation and solidarity. One may wonder: how can such a mutual agreement come into fruition between a fish and some bacteria which are deprived of a nervous system, mind, and consciousness?

One of the reasons that marine biologists are interested in light-emitting bacteria is the wide-lit regions called the “Milky Seas.” These can be observed in satellite images of Earth. Recently, satellites helped detect a bioluminescent area of roughly 5,946 sq. mi in the Indian Ocean; scientists wondered if some bioluminescent bacteria or Dinoflagellate-type flame-colored algae may be the cause of the phenomenon.

Alarming jellyfish

The luminescence of some marine life serves as an alarm or distress siren. A remarkable example of this is the Atolla jellyfish (Atolla wyvillei), an elegant inhabitant of deep waters. This jellyfish produces blue lights that are spread in circles in the water when it is attacked. Thanks to these lights, it tries to draw the attention of larger and stronger animals than the initial attacker in order to escape from harm’s way.

As can be observed in some species that we are familiar with, such as fireflies, the bioluminescence feature that is full of wisdom granted to some living beings is a thought-provoking biological miracle which does not only make us ponder where they got these abilities from but also reveals how so many intricate patterns are found in nature.

References

• Steven H.D. Haddock, Mark A. Moline and James F. Case. 2010. Bioluminescence in the Sea, Article in Annual Review of Marine Science, DOI:10.1146/annurev-marine-120308-081028 Source: PubMed.
• Edith A. Widder. 2001. Harbor Branch Oceanographic Institution, Fort Pierce, Florida, Marine Bioluminescence, Bioscience Explained, vol 1, no 1, pp. 1-9.
• Edith A. Widder. 2010. “Bioluminescence in the Ocean: Origins of Biological, Chemical, and Ecological Diversity,” Science, vol. 328, pp. 704-708.
• www.wired.com/2012/01/glow-little-spewing-shrimp-glow/ March 28, 2018.
• en.wikipedia.org/wiki/Malacosteus_niger / April 1, 2018.
• Harold, A. 2015. Malacosteus niger. The IUCN Red List of Threatened Species 2015: e.T190149A21909439. http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T190149A21909439.en.
• https://www.iucnredlist.org/species/190149/21909439

Have you ever seen a rainbow? Until recently, I had looked at many rainbows, but had never truly seen a rainbow.

In his writings on faith and logic, religious scholar Bediuzzaman Said Nursi maintained that looking and seeing are two different things. In his book, The Words, he says: “The eye is a window through which the spirit looks at this world. If you use it on behalf of your carnal soul, without selling it to God Almighty, by gazing at transient, impermanent beauties and spectacles, it panders to lust and other carnal desires.”

Using Nursi’s reasoning, you might look at a magician who is right in front of you, for example, but never see how a trick is accomplished. The same thing happens when you look at a mathematical equation but don’t see what the x value is – unless you are good at mathematics.

After watching MIT physics professor Walter Lewin’s lecture “The Hidden Beauty of Rainbows,”[1] I am finally able to see the rainbow, instead of just looking at it. To share my fascination about this topic, and reinforce my own knowledge, here are some notes I took during Lewin’s lecture. Walter Lewin is the author of For the Love of Physics. This book is really a perfect book if you love Physics.

Figure 1.0

There are four fundamental facets we need to cover to understand a rainbow (Figure 1.0). The first is the “radius” of a rainbow. Since every rainbow has a radius, this means a rainbow is a circle. And every circle has a center point. A rainbow’s center point is below the horizon. Here, we can ask these follow-up questions:

1.1 How we can find the radius of a rainbow in degrees?

1.2 Do all rainbows have the same radius?

The second question is about the colors of a rainbow, specifically red. If you see a rainbow, there is always a red color. But:

2.1 Is the color red always on the inside or outside of the rainbow?

2.2 Does the position of the red color depend on the time of the day and year?

It’s obvious that light determines a rainbow. If there is a rainbow somewhere, there is an enormous difference in the brightness of the sky above and below a rainbow. We can now ask:

3.1 Where is it bright?

3.2 Where is it dark?

There are some additional questions we need to discuss regarding the second bow in Figure 2, specifically:

4 Have you ever noticed the second bow? If yes, then;

5 Where do you look for the second bow?

6.1 What is the color sequence of the second bow?

6.2 Is it the same as the primary bow, is it brighter, or is it reversed?

Figure 2.0

In order to understand rainbows better, we need to review some basic physics. Let’s start with reflection and refraction.

Mediums, reflection, and refraction

Definition: A medium[2] is the substance that carries a wave from one location to another.

When light goes from one medium to another, like from air to water, one of two things happens:

● Some of that light bounces back, which we call reflection. The light will reflect at the same angle at which it hit the surface.

● Part of the light doesn’t reflect, instead continuing into water at an angle. We call this refraction.

Each medium has an index of refraction, which tells us what the speed of light in that medium is. The index of refraction of air is 1.0003, and the index of refraction of a vacuum is 1.

That means the speed of light in air and in a vacuum is almost the same. That speed is 300,000 kilometers per second, and that’s why the index of refraction for air and a vacuum is 1. But in water, the index of refraction is approximately 1.33. The difference between 1 and 1.33 means that in water the speed of light is 33 percent slower than it is in air.

Snell’s law and an angle of incidence

There is also a connection between angle of reflection, angle of refraction, and the index of refraction. We call it Snell’s law.

Snell’s law illustrated:

Figure 3.0

To understand this formula, you need to know the definition of the sine of an angle.

Definition:The sine[3] is a trigonometric function of an angle. It is found by taking the length of the side opposite the angle and dividing by the length of the longest side of the triangle.

If α is 0°, then sin (α) = 0.

If α is 30°, then sin (α) = 0.5.

If α is 90°, then the sin (α) = 1.

Let’s do an example where we can apply Snell’s law (Figure 4.0).

Light comes from air to water at an angle of 60°. (This is possible, because the angle at which water comes in, the angle β, will be 40.6°.)

Definition: The angle of incidence[4] is the angle between the incoming light and the vertical on the surface.

Figure 4.0

Like professor Lewin said, “very simple, very straightforward.”

Figure 5.0 | Figure 5.0. Example of refraction and reflection. See also [5].[5]

Figure 6.0

Figure 6.0 displays a true wonder of water. Sunlight is coming from the left side, landing everywhere on half the surface of that raindrop. We can choose one very narrow beam of all that sunlight with a 60° angle of incidence. We call the angle of incidence “i” and the angle for the refraction “r.”

Of course, that narrow beam is the only a small fraction of the total.

At point A, two things happen (in accordance with Snell’s law);

● A little bit of light reflects.

● The remaining light refracts.

The light reaches point B inside the water drop. At point B, two things happen:

● Some of the light goes back into the air (signaling refraction).

● Some of the light gets reflected. (Therefore, at point B, the angles are the same, “r.”)

Then the reflected light goes on its way to point C. Here, a little bit of the light is reflected and goes back into the water. Most of it comes out of the water, which results in refraction.

At this point, if we use Snell’s law at point A, the reflection law at point B, and then Snell’s law at point C again, we will see that our angle for the refraction at point C will be, surprisingly, “i.”

Now, if we check the line that comes out from the water at point C, we will have a changing angle. We can call it φ (Phi). And for the angle φ, we have an algebraic formula, as follows:

φ= 4r — 2i

If you check the figure, you will see that we have 4 r and 2 i.

By the way, if we take the narrow beam which passes through the center of the raindrop, we can easily see that the angle of incidence is zero. In accordance to Snell’s law, this narrow beam goes straight through. Then it reflects back and finally it comes out of the water. This is true because:

if i = 0, then r = 0 and therefore φ = 0.

Let’s do something interesting and change the value of “i.” If the light hits the water drop higher up, the angle “i” increases. At some point, the angle φ also increases and reaches a maximum value.

Figure 7.0

If you recall, the index of refraction for water is 1.336. If we take any value of “i” on the table and apply Snell’s law, we can easily calculate values of r. And then, if we use the formula φ=4r — 2i, we can come up with the values of φ. This is illustrated in Figure 7.0.

If this doesn’t seem all that special, there is something else that you wouldn’t expect: φ reaches a maximum value, and when you go to higher values of i, then φ goes down again. This plays a key role in the formation of a rainbow.

The index of refraction depends on the color of the light.

Figure 8.0

As seen in the table, when the angle of incidence for red light is very close to 60°, the value of φ is at its maximum, which is 42.3°. In other words, the value of φ can be smaller than 42.3°, but it cannot be larger. For blue light, the angle of incidence is slightly lower, and the φ maximum is at 40.7°.

Water drop and a cone

A key question arises: Let us say we have one water drop, and the sunlight falling onto that water drop is coming from the left. What is that one water drop going to do with the white light from the sun that covers half of the rainbow?

Let us check first for red light and then for blue light.

Light beams will come out of this drop, and that cone will be filled with red light. But the angle for the light beams cannot be larger than 42°, meaning they can be smaller. Then we will see a cone of lights.

But why is it a cone? Because, if we go back to what was previously discussed, we will remember that one light beam comes in with an angle i, and then comes out with an angle i.

Figure 9.0

Figure 9.0 shows a representation of a water drop. The light that comes in at the angle of incidence is 60°. It refracts and reflects inside the droplet, then goes to point C and comes out of droplet at an angle of 42°. And, surprisingly, if the angle of incidence is 60°, when the light beam comes out, it has to be red light. On the other hand, there is not only one light beam coming in with an angle 60°. The entire surface of this water drop is illuminated by the sun, so there are an enormous number of beams for which the angle of incidence is 60°.

If we go back to Figure 9.0, we see the black line on this water drop. Any light beam that comes in anywhere on that black line will have an angle of incidence of 60°.

Figure 6.1

Now we will do the same for blue light. This time, we will have another cone which is completely filled with blue light, but when the blue light beams come out, the angle will be at a maximum of 40.7°.

Interesting fact: All the colors except for red and blue that are in the sunlight will be in between the red and blue.

Figure 6.2

A journey: refraction, reflection, and refraction

We know that when the light comes in, it goes through a journey. A light beam refracts, then reflects, and then refracts. That’s all. But, how about the light on the right side of the cone? Is there any light? When the sun shines in, does this water drop bring light there?

If the angle φ is larger than 42°, then, yes, it is possible. But we have already proven that the angle φ cannot be larger than 42°. So, it is impossible: There is no light outside the cone.

Another question… What will be the color of the light inside the blue cone? We should remember that the red light is everywhere in this cone, because as long as the angle φ is smaller than 42°, red light can be anywhere. The blue light is also almost everywhere because the blue light is allowed to be smaller than 40°. This means all the colors that we didn’t mention are coming out inside the blue cone and there will be just white light.

Figure 6.3

To summarize, if we have a water drop, and a bright light shining onto this water drop, we will see red, blue, green, white, and other colors inside the cone or circle. In other words, all the colors of a rainbow. And of course, there will be no light outside the cone. There are some experiments on YouTube that you can watch if you want.

Figure 6.4

You may think that at the location where blue comes out, if all the other colors can come out — which they can because the angle is smaller than 40° — the light should be also white, not blue. It is a nice approach, but wrong.

It is wrong, because of the light intensity. If you check the graph for the intensity of the light, you will see that different colors have peak points where φ reaches the maximum value. If all the colors are present and equal intensity, we see white light. That’s why the inside of the cone is white. However, when the color red spikes up, it dominates its location. We don’t even notice the other colors.

Figure 6.5

Looking at the sky

Let’s say you are standing at point A and the sunlight is coming from the left. Since the light comes from infinitely far away, all these lines are parallel to each other. Let’s say you look at the sky in direction B and pick a raindrop at any point. Any point you pick will cast the cone in the direction of the sun with the angle 60°.

When you look at the sky in the direction B, will you see light? You will not, because you are outside the 42°.

Figure 10.0

What if you look in a different direction? We will look at point C (it doesn’t matter where), and take a rain drop on line C. Light beams will do the same thing. Again, they will produce a 42° red cone. However, you will see white light. Yes, you read that right, white light, because you are looking straight in the middle of the cone of white light.

Let’s say we choose another angle and look at point D. If we choose a raindrop anywhere on line D, it will make no difference. It will cast into the sky the famous 42° angle because that’s the angle that was chosen there. If we look in that direction of the sky, what will we see? Yes, only red. No other color!

Figure 10.1

And now, we know where we will see red light, blue light, or white light. And we also know which direction has no light.

A rainbow is a bow in the sky

Let’s suppose the sun is on your left and you are standing at point A (Figure 11.0). Since there is light, you will have a shadow on the ground. As long as you look 42° away from any direction, you will only see red. That is because a cone is a spherical object. And that explains why the rainbow is a bowl in the sky. As long as it is 42° away from a line in any direction, you will always see red light. And if you decrease the angle, you will see the other colors in the sky.

And so now, we can make a picture of a rainbow.

When we look at the horizon, sometimes we see a rainbow. And we will have a center point somewhere below the horizon. The radius with 42° has red light. The blue light is closer to the 40° radius. This tells us that the red bowl is always on the outside and the blue light is always on the inside. That’s what we always see.

Figure 11.0

Double Reflection in the Rainbow

We can also include two reflections in the rainbow. If we do, we get refraction, reflection, another reflection, and then another refraction. So, the light beams reflect twice. And if we do this hocus-pocus again and again, we can come to a conclusion: There is no maximum value for the various colors, but there is a minimum value. In other words, various colors cannot be lower than a certain value, but they can be higher.

And if we do some calculation for the angles, we will see something very similar. We will find out that the second bow is pointing at the sky, and the angle is 10° above the first one (which is 52°). And, surprisingly, the colors of the second bowl reverse. In other words, red is the one on the inside, and blue is on the outside this time.

Figure 11.1

Interesting fact: There is no light between the two bowls. This is because of the φ maximum and minimum. We call that dark part Alexander’s dark band.[6]Additionally, since the second bowl is formed by φ minimum, sunlight can come out at angle φ or larger and there will be sunlight above a rainbow.

Figure 11.2

Some examples…

Image 1: René Descartes’ sketch of how primary and secondary rainbows are formed (probable engraver: Frans van Schooten the younger).

Image 2: This diagram was drawn by the famous physicist Newton who was one of the first to understand the rainbow, from his book Optics.

Image 3: Double rainbow. The primary red bow is on the outside, and blue is on the inside. Alexander’s dark band can be seen in between the two bows. It shows up really dark. For the secondary bow, red is on the inside, and blue is on the outside.

Image 4: Walter Lewis’ backyard and his rainbow. When you water your garden when the sun is high in the sky, you can get a rainbow all the way around you. 42° away from the line is always red. If you turn around and look back, it is red.

Image 5 | A white rainbow. It is very unique and rare. It is also called a fog bow, because fog has small water droplets that create this effect.

Image 8 | Red rainbow. Let us imagine that there is a rainbow at sunset. What would you expect to see? We would only see red light because there is only red light. What would happen to the white light inside the bow? It would be red too.

Southern Pine Beetles (Dendroctonus frontalis, figure 1) are one of the most harmful pests in the world, causing hundreds of million dollars worth of damage to pine trees in the Southern United States. These beetles initiate their attack on a pine tree by having a small group of female beetles dig into the inner park (Figure 2) and phloem of the pine tree. Once this work is done these females will secrete a chemical that will draw other male and female beetles to the affected pine tree. This initial attack is followed by a massive attack by a larger number of beetles, enabling them to easily overcome the defenses of the pine trees due to the sheer number of beetles. Shortly after taking over the tree, mating begins between the male and female beetles. As part of the mating process the females fill the excavated galleries within the trees with eggs. After the eggs have been laid the adult beetles will then leave the tree and continue to attack other trees. Attacking trees and causing their death is of course a sad story and may not sound very interesting since most pests have similar attack strategies; however, one detail that we did not mention yet makes this process more intriguing. What do the larvae eat to complete their development within a gallery that is inside a dead tree? The answer is: Fungi.

Pine beetles establish a symbiotic life structure with a beneficial fungus (Entomocorticium sp. A), which is the main food source for their larvae. Adult pine beetles have a body compartment (mycangium), in which they can carry this fungus. When adult beetles dig galleries in tree barks, they inoculate these galleries with the fungi. This fungus will grow in these galleries that helps the beetles’ larvae complete their development by providing them with a source of nutrition. Fungi also benefit from this process by being transferred from one tree to another with the help of the beetles. This symbiotic life structure is threatened by the existence of an antagonistic fungus, (Ophiostoma minus, also known as blue stain fungus) and parasitic mites both of which the southern pine beetles also bring along. The blue stain fungus has no nutritional importance for larvae, this fungus can grow in the same galleries as the beneficial fungus and they can even outcompete them. In addition, the parasitic mites feed on the blue fungi and can prove harmful beetles as the amount of blue fungi increases. Therefore, beetles’ larvae cannot survive for long and thus the reproduction of the southern pine beetles can be disrupted without some form of defense.

A recent study by Scott et al. has shed some light on this complicated life structure [3]. These tiny beetles, which are only a few millimeters long, have a smart defense mechanism to prevent their larvae (Figure 3, pink arrow). As far as the history tells us, humankind started using pesticides about 5000 years ago, but these tiny beetles have been using them for preventing the growth of the blue-stain fungi long before humans started using pesticides. These studies showed that the symbiotic coexistence of southern pine beetles and the beneficial fungi (Figure 3, yellow circle) is maintained by a (actinomycetous) bacterium (Figure 3, inside the red square). This bacterium produces a previously unknown antibiotic compound (named mycangimycin), which selectively inhibits the growth of blue-stain fungus hence providing a significant advantage for the maintenance of the beneficial fungi (that is, the main food source of the larvae). How can this bacterium even be present in the freshly carved galleries in pine trees in the first place? The surprising answer to this question is that they are transferred to these galleries by the very same pine beetles. As mentioned earlier, adult pine beetles carry beneficial fungi in their body compartment (mycangium) and inoculate the galleries they carved with this fungus to provide food for their larvae. In addition to this beneficial fungi these beetles carry they also carry bacteria that can produce antibiotic compound to inhibit the growth of blue-stain fungi and consequently diminish the number of parasitic mites. This bacterium can grow inside these galleries and even in a body compartment of adult southern pine beetles. Interestingly, this antibiotic kills blue-stain fungi but does not significantly affect the growth of the fungi, which is the food source for larvae. Thus, the beneficial fungi can multiply in number and offer enough food for the development of beetle larvae. Some of these larvae manage to grow to adults and then leave to attack other pine trees carrying the same fungi and bacteria with them (Figure 4).

The interactions within the rest of the life kingdoms is not any less complicated than the symbiosis between pine beetles, fungi, and the bacteria. The interactions between animals, plants and microbes are very complex and also fragile. Removing or replacing any member of an ecosystem can often result in a serious failure in the ecosystem as was observed many times especially within the last century.

References

1. http://www.nsf.gov/news/news_summ.jsp?org=NSF&cntn_id=112319&preview=false.
2. http://entnem.ufl.edu/creatures/trees/southern_pine_beetle.htm.
3. Scott, J.J., et al., “Bacterial protection of beetle-fungus mutualism.” Science, 2008. 322 (5898): p. 63.

We all know that it is essential for life. However, probably because of its abundance and simple chemical composition, we often regard this tasteless and odorless substance as being important, but quite simple and ordinary. Scientifically, it is the exact opposite. It appears to show extremely complex and unusual behavior. It is the most studied substance on Earth. Yet, scientists are still puzzled over its strange properties. Even the best computers we have today cannot simulate all of the different properties of water.

Let us look at an example of the surprising properties of water. The strangeness of water starts with the fact that it exists on Earth. Water, being composed of two fairly light atoms (hydrogen and oxygen), should be in the gas phase at the usual temperature ranges that exist in our world. In fact, all compounds that are close to it (i.e. H2S, H2Se, and H2Te) are found mostly in the gas phase. But, compared to similar substances, it melts about 100 degrees above the expected melting point and it boils about 150 degrees above the expected boiling point (see Figure 1). The result is that it is the only material that exists naturally in all three forms (i.e. as ice, liquid, and vapor) on Earth.

In addition to the example given in the previous paragraph, water has at least 40 different surprising properties (See for example the “Forty-one anomalies of water” section in Ref 1). But, what is even more astonishing is the fact that most of these anomalous properties of water are absolutely crucial for life. Simply stated, life on Earth depends on these extraordinary aspects of water. Below we will discuss some of the anomalous properties of water and their importance for life. At the end we will briefly try to explain why water behaves so differently.

1-Water Has an Unusually High Heat Capacity

Heat capacity is a measure of the ability to store heat. Formally, it is defined as the amount of heat required to raise the unit mass of a substance by one degree of temperature. If the heat capacity of a substance is high, it will store heat well, i.e. its temperature will not rise much for a given amount of heat. Water has the highest heat capacity among common substances. This has a crucial impact on our life.

It is thanks to this fact that living organisms, which are mostly composed of water, can regulate their body temperature easily. For example, the human body needs to keep its temperature between 36.1 and 37.8 °C. This is only possible because it is composed mostly of water. Since the heat capacity of water is unusually high, even if the temperature of the environment changes greatly, the heat exchange between the body and the environment does not cause a great change in body temperature.

Another consequence is the moderation of the climate near large masses of water. The heat capacity of land is much less than that of water. This is why the temperatures of oceans tend to vary much less than that of land. The temperatures in the oceans vary between -2 0C and 35 0C. On land, temperatures may vary anywhere from -70 0C to 57 0C. Compare also the Moon, which has no water. Temperatures on the Moon range from -155 0C to 135 0C.

In addition to having a great heat capacity, water conducts heat more easily than any other liquid, except mercury. This makes the temperature quite uniform in living organisms. Also, the vertical temperature profile in oceans and lakes is essentially uniform due to this fact.

2- Water Has an Unusually High Heat of Evaporation

When a liquid evaporates, it absorbs heat from the environment. This energy is used to transform molecules into gas form. The heat of evaporation is defined as the amount of heat required to convert a unit mass of liquid into gas. Water has an unusually high heat of evaporation compared to most other common substances. It is so great that you need to supply about five times the amount of energy to evaporate water that is needed to heat it from 0 to 100 0C.

This fact is crucial for the evaporative cooling system of the human body and animals. When we sweat, the sweat absorbs heat from the body in order to evaporate. Since water has a very high heat of evaporation, effectively a large amount of heat is removed from the body through sweating. That is why when we engage in physical activity we sweat. Excess heat in the muscles is easily removed through the evaporation of sweat thanks to the high heat of the evaporation of water.

The high heat of evaporation also prevents dehydration. If it were low, water would then evaporate easily from the body and we would quickly dehydrate.

3- The Density of Water Behaves Unusually as a Function of Temperature

The density of almost all other liquids decreases with increasing temperature. Water is an exception to this. Starting from 0 °C, the density of water increases, and reaches a maximum at 4 °C, decreasing afterwards. Also most other liquids become denser when they condense, but water is an exception to this as well. The density of ice is less than the density of water, which is why ice can float on water.

Both of these exceptions turn out to be extremely important for underwater life. When the weather gets cold near a lake, first the temperature of the lake’s surface starts to decrease. As the temperature of the surface cools to around 4°C, it becomes denser and can move downwards, letting the warmer water reach the surface. Therefore, before the lake can start freezing almost all of the water in it needs to be cooled to approximately 0 °C. If there was not an anomaly at 4 °C then water would begin to freeze from the surface before the entire lake cools to 0 °C. Since water has an enormous heat capacity, the necessity for the entire lake to cool to approximately 0 °C before any freezing can occur delays the freezing considerably. It is also crucial that the density maximum in water is near freezing point, not at any other point.

When the temperature finally gets to 0 °C and the water start to freeze, it will start to freeze on the surface. Since ice is less dense than water, it will float on the surface and will not sink to the bottom. And once a surface layer of ice is formed, it will protect the rest of the lake from the environment and no further freezing will occur. There would not be any underwater life if ice formed on the bottom. It would also take forever for the ice to melt if it was formed on the bottom rather than on the surface.

The fact that water expands upon freezing is also important for the formation of soils. When the water freezes inside a rock, it can easily crack it into pieces, just like a soda placed in the freezer explodes upon freezing. Therefore, one of the most important steps of soil formation is dependent on this exceptional characteristic of water.

4- The Absorption Coefficient Anomaly in the Visible Region

Another interesting property of water lies in its absorption of light. Every

substance has a characteristic absorption spectrum that shows how much light at a particular wavelength is absorbed. If the absorption coefficient is high at a particular wavelength then the material will look opaque at that wavelength. If it is low, light at that particular wavelength will be transmitted and the material will appear transparent.

In Figure 2, the absorption coefficient of water is plotted as a function of wavelength (red line). The first thing you notice is that water has a very high absorption coefficient, except for a very narrow region around 500nm. In this small region of wavelength, the absorption coefficient is ten million times smaller than the neighboring regions. What is more interesting than this enormous drop in the absorption coefficient is that this dip happens exactly at the visible part of the spectrum. The human eye can only see wavelengths between 400-700 nm. This visible part of the spectrum is indicated by a rainbow colored strip in the graph. It is amazing that this exactly coincides with the region where water is transparent. Adding to this pleasant surprise is the fact that the amount of light emitted by the sun peaks around this dip as well.

Everything is conveniently adjusted for the habitants of this blue planet. The maximum intensity of emitted sunlight happens to be in the narrow range of the spectrum that we can see. And water on the atmosphere lets this part of the spectrum through thanks to the strange dip in the water absorption spectrum. Worried about the dangerous UV radiation from the sun? This is taken care of too. Just below the visible region, the absorption coefficient of water is ten million times higher. So water vapor in the atmosphere very effectively removes most of the dangerous UV light and shields us.

The spectrum of the light from the sun, the absorption spectra of water and the visible region of the spectrum that we can see are all physically independent phenomena. Yet, it is worth noting that each of these phenomena behaves in such a way that it seems they should have a precise knowledge of each other. If you think this is too much of a coincidence, there is even more. Water is also designed to maximize our visual pleasure. You are probably astonished by the lovely color match between the blue sky and the blue sea. Most people assume that this is because the sky is blue and the sea appears to be blue because it reflects the sky. In fact this is wrong. Water is blue since its absorption coefficient is higher in red; therefore it absorbs more red and reflects the blue part of the spectrum. This can be seen in Figure 2, in which the absorption coefficient in the red colored segment of the rainbow strip is more than 100 times greater than the blue part. The sky is blue for an entirely different reason (since it is blue light that is scattered the most by the nitrogen in the atmosphere). Again two very different, independent physical phenomena are at work here, but the result is a pleasant view for us.

Why is Water so Strange?

Most of these unusual properties of water are the result of the collective behavior of water molecules. That means that one cannot understand them just by thinking about a single H2O molecule. A single H2O molecule is a polar molecule: the two H atoms are slightly positive and the O atom is slightly negative. So when you put these molecules close to each other, the positively charged H atoms are attracted to the negatively charged O atoms of the neighboring water molecules. This is called “hydrogen bonding.” Because of this, molecules tend to order themselves rather than moving randomly, even in liquid water.

Hydrogen bonding is thought to be responsible for most of water’s strange properties. This is why, for example, water has a high boiling point and a high heat of evaporation. Extra energy needs to be supplied to break the hydrogen bonds before boiling and evaporation can occur. Another example is the high heat capacity. As water absorbs heat, it stores this as potential energy by breaking hydrogen bonds without considerably increasing its kinetic energy. This leads to a small temperature increase, therefore a high heat capacity is created for a given amount of heat.

But not all of the anomalous properties of water are that simple. Some of them are not even understood today, despite a considerable amount of current research. For example, water seems to play a crucial role in protein folding. Protein folding is the process by which each protein acquires a unique three-dimensional shape. And it can only function effectively in this particular shape. Despite millions of different possible folding configurations, a certain protein will always fold into its unique structure within milliseconds. But how can a protein always find its way to the same configuration? Water comes into play at this point. It is thought that the hydrophobic (water repelling) interactions between water and protein molecules and the hydrogen bonding interactions in water are major driving forces in protein folding. The exact details of this are still not known. Understanding them is the key for understanding many diseases and developing drugs.

In summary, water is central to our lives. It accounts for a large proportion of our bodies, we drink it, fish in it, and wash and swim in it. But we usually are unaware of how remarkable it is. Here, we have given only couple of examples of the anomalous properties of water that are also crucial for life. Scientifically, our understanding of water is far from being complete. It seems, as the research continues, that the already long list of mysterious aspects of this miraculous substance will get even longer as we learn more about it. On the philosophical side, it is interesting to note that a very simple molecule (H2O) has been selected as a means to do all of these vital, complicated, and unrelated jobs, all at the same time through its unexpected and surprising properties. 

References 

• “Water Structure and Behavior,” Martin Chaplin, www.martin.chaplin.btinternet.co.uk
• Segelstein, D., 1981: “The Complex Refractive Index of Water”, M.S. Thesis, University of Missouri-Kansas City.
• www.biology.arizona.edu/biochemistry/tutorials/chemi stry/page3.html
• www.hyperphysics.phy-astr.gsu.edu/hbase/chemical/water.html
• “Water – The Marvellous Molecule”, BBC TV program.
• www.bbc.co.uk/worldservice/programmes/archive/030430_molecule.shtml

Light reveals a world of colors by painting everything it touches. Our plain and soulless furniture gains meaning. Our brown bookshelf, gray study table, green mug carpets, rugs, curtains the yellow wheat fields in the harvest picture, the blue china vase, our favorite brown sweater the striking green of a tree surrounded by concrete buildings, the blue sky, and the carousel of life that becomes worth living by being embellished with colors.

Let’s travel through the wonderful world of colors. Each color conceals a story. Some virtuous and sensitive eyes see the truth through them, while others see rage, anger, and all the evils dictated by the alter ego. Colors carry such feelings as anger and hope, and symbolize such concepts as sinfulness and innocence. They are abused or sacrificed, and widely preferred or despised.

Literally, color is a phenomenon of light or visual perception that enables people to differentiate otherwise identical objects. Being one of matter’s distinguishing characteristics, in a sense its meanings are the meanings of life. As truth is interwoven with life, truth might be viewed through colors.

Their Influence on People

The most important aspect of color in daily life is probably the aesthetic and psychological responses that they evoke”our psychological perception”and the resulting influences on art, fashion, commerce, and even physical and emotional sensations. For example, reds, oranges, yellows, and browns are warm, whereas blues, greens, and grays are cold. Reds, oranges, and yellows are said to induce excitement, cheerfulness, stimulation, and aggression; blues and greens to induce security, calm, and peace; and browns, grays, and blacks to bring sadness, depression, and melancholy. However, we can only generalize about such subjective perceptions.

Age, mood, mental health, and other factors affect color perception. People sharing distinct personal traits often share color perceptions and preferences. For example, schizophrenics are said to have abnormal color perception, and very young children learning to distinguish colors usually prefer red or orange. Many psychologists believe that analyzing one’s use of and response to color reveals relevant physiological and psychological information. Some even suggest that specific colors have a therapeutic effect on physical and mental disabilities.

In China, India, and Japan, colors are used in alternative medicine. Orange is considered good for depression, yellow for diabetes, green for ulcers and spiritual fatigue, and blue-violet for epilepsy. What is important here is the body’s receptor of color, such as eyes or skin. Each color’s wavelength carries and transmits energy to the bodily part having that color. This energy removes physical and emotional disorders, and colorful rays directly influence the neural system. Thus, different illnesses are treated with different rays of colors having different tones and impacts.

Although these medical benefits are still in question, color does cause definite physical and emotional reactions. Rooms and objects that are white or have light shades of cool colors may seem larger than those with intense dark or warm colors. As designers and decorators know, black or very dark colors have a slimming or shrinking effect. A cool room decorated in pale blue requires a higher thermostat setting than a warm room painted pale orange to achieve the same sensation of warmth.

People viewing unusual colors produced by special illumination may experience headaches and nervous disorders. Tasty wholesome food served under such conditions appears repulsive and may induce illness. Other colors induce pleasure. When an affectively positive or pleasurably perceived color is viewed after a less pleasant color, it produces more pleasure than when viewed by itself. This effect is known as affective contrast enhancement.

What Colors Have Experienced

Colors are not universal. Some languages do not have separate words for green and blue or yellow and orange, whereas Eskimos use 17 different words for white to describe different snow conditions. Comparing color terminology reveals certain consistent patterns. All languages have designations for black and white.

If a third hue is distinguished, it is red; next comes yellow or green, and then other colors.

Consider soccer fanatics who so love their team’s colors that they tear and burn the other team’s flag. They dye their hair and faces yellow-red, blue-white, or red-white to match their team’s colors, but cannot stand the opponent’s colors. They taunt the opposing team with clothes in their own team’s colors, even to the extent of injury or death. Most important, they gain identity, send a message, and enjoy the confidence that comes with belonging to a peer group.

Colors are gifts, not a cause of separatism. As sociologist Orhan Kologlu points out, people of different religions and nations chose different colors. In the Balkans, blue and white are considered to be Greece’s colors (its flag is blue and white). During conflicts, people do not use the colors of other nation’s flags. But this is emotional and irrational, for no nation owns a color. During a time of Turkish“Greek tension, red-white clothes were despised in Greece, and blue-white clothes in Turkey. Bulent Ecevit (current prime minister of Turkey) broke a taboo with his poem Blue Magic, which contains the lines: Like a blue magic, lies a warm sea between us / We are two nations, as beautiful as the other, at its shores. He also chose blue and white as his political party’s colors. Ironically, this party whose emblem is in Greek (!) colors now is now in power Turkey.

A nation’s color choices change over time. Ancient Turks considered blue as sacred, for it was the color of the sky. Some Turkic nations still use it as their national color. In medieval Europe, blue stood for nobility and aristocracy, and the latter were believed to have blue blood. But in America, blue is associated with low spirits, melancholy, and depression (a blue funk). For women it means learned and intellectual, while in morality it means puritanical. It also means profane or indecent (blue movies), off-color or risqué (blue jokes), and a kind of music (the Blues) dominated by sad and melancholic themes.

Red and black are most commonly associated with sociopolitical conflict. For years red symbolized violence, pillage, murder, oppression, anti-democracy, and terrorism. In emotional terms, it means a face flushed with anger or embarrassment (red in the face), or bloody (red eyes).

In politics, it means inciting or endorsing radical sociopolitical change, especially by force, as in red uprising or anything associated with communism (the former USSR’s Red Square). There are even two Red armies: the Soviet army established after the 1917 Revolution, and the Japanese Red Army formed in 1969. The first was renowned for its strict penal codes and discipline, such as punishing battalions by sending them on suicide missions. New regulations in 1960 considerably lightened the Soviet Army’s redness. The second army, a small-structured Japanese terrorist organization, remained active until 1990.

Italy’s Red Brigades, an extreme left-wing terrorist organization, chose red and violence as it sought to prepare 1970s Italy for a Marxist uprising. Chinese revolutionaries seeking to end China’s traditional culture chose red and violence, as did Cambodia’s radical Khmer Rouge (Red Khmers). This latter group massacred an entire generation, an estimated 1.5 million people out of an estimated population of 5.7 million, during their 3.5-year reign. 

It is used for heavy or serious (black intrigue); dirty and soiled (black hands); thoroughly sinister, evil, or wicked (black deed); negative (a black mark in one’s record); the supernatural or Satan (black magic); very sad, gloomy, or calamitous (black despair); a disaster (black Saturday); hostility, angry discontent, sullenness (black resentment); grim, distorted, grotesque satire (black humor); or covert intelligence operations (black government missions).

Although we associate black with negative meanings, we cannot deny that it also symbolizes seriousness, respectability, and nobility. There are occasions when white, the symbol of purity and innocence, is inappropriate says social psychiatrist Ibrahim Ballioglu. Colors should be used with the proper tones and combinations. He claims that it is logical to associate white with positive and black with negative concepts. Black and white are like night and day. The dark of night scares people, whereas the light of day relieves them. The colors hidden at night come forward in daytime. People are inclined to like light and bright colors. We apply white light in our depression patients’ therapy. One’s interest in dark colors gives clues about one’s mood. A patient’s wearing white signals that he or she is getting well.

In history, such groups as the Black Hand,1 Black Faces, and Black Shirts favored violence and vandalism. Mussolini’s fascist Black Shirts group is the most interesting. After his overthrow 1943 and the Black Shirts’ dismissal, people avoided wearing black shirts.

White means free of color; light or pallid (white hair, lips white with fear); without spot, blemish, or moral impurity; innocent or chaste (white wedding); harmless (white lie, white magic); and favorable or fortunate (white days of life). It also means politically conservative or reactionary people who undertake counter-revolutionary measures (white terror). In music, it is associated with a musical tone quality characterized by a controlled pure sound and a lack of warmth, color, and resonance.

Green means mild and clement (green winter); pleasantly alluring; youthful and vigorous; not ripened or matured (green apples, tender green grasses); fresh and new; marked by a pale, sickly, or nauseated appearance; envious (green with envy); somehow deficient or unsophisticated; and an environmentalist political movement (Green Peace) or individual working to preserve environmental quality.

Yellow is associated with sensationalized scandal items or distorted ordinary news (yellow journalism), and cowardice (a yellow streak up one’s back). Pink signifies moderately radical and usually socialistic political or economic views, as well as emotional excitement (tickled pink).

Do Nations or Religions Have Their Own Color?

Color harmony, preferences, symbolism, and other psychological aspects are culturally conditioned and vary with time and place. For instance, American and Japanese concepts of warm and cold colors are essentially the same. However, Japanese consider blues and greens good and the red-purple range bad, while Americans consider the red-yellow-green range good and oranges and red-purples bad. In the West, black signifies mourning; other cultures use white, purple, or gold.

Orhan Kural says that societies tend to use colors that comply with their culture and belief: In Indonesia’s Banggai Islands, people believe that their ancestors arrived in brown canoes. Their houses look like brown-painted canoes. They sacrifice a water buffalo and hang its head at their doors to make funerals more elaborate. During these rituals they wear red. Since the streets are filled with blood, red is dominant in their culture. In Mongolia, green is dominant. Mongolians has five times as many animals as people. I think they paint their tents and furniture green due to their love of animals and nature. In Guatemala, the Spanish invaders forced each clan to wear a different color in order to differentiate them. This seems to be welcomed and accepted by the people, for it remains in force. All women I saw in the bazaars wore the same color. The city of Varanasi in India and the sacred Ganj river reminds me of orange, and the Taj Mahal reminds me of white.

Nevval Sevindi, who lived in Iran for some time, says that Iranians consider black to be holy and noble. According to her, Iranians and Westerners both see black as a symbol of mourning. Iranians use black to commemorate their Imams, and Westerners wear it at funerals and to commemorate their saints.

It seems that they are always mourning, since they keep Karbala’ alive in their memories.2 Red is a color of disgrace in Iran. However in Turkey, China, and India, red is the color of weddings. In Turkey, the bride wears a red veil over her head on the eve of the wedding day and a red belt on the wedding day. Women wear a red ribbon after giving birth. Red means a new future and abundance. Turks do not consider black the color of mourning. They attend funerals in ordinary clothes, for death is an ordinary part of life. Africans and Asians like to wear many colors. I associate this with their living in bright and sunny countries and within nature. Sunlight affects their clothes and moods. Violet is the Byzantine Empire’s color, for only the emperor wore it. This tradition continued after the emperor’s death, for his grave was built with violet porphyry stones, says Sevindi.

Tumulus-hillock excavations in Tekirdag, Turkey, reveal that Alexander the Great’s father wore mostly purplish colors, like that of a judas-tree. Maybe this is why Byzantine emperors valued purple tones so much. Other researchers give different reasons. For instance, historian Haluk Dursun states: There is a belief in Christianity: Judas Iscariot, one of the 12 apostles of Jesus Christ, betrayed him at the Last Supper. Romans arrested and crucified Jesus. Judas, full of regret, hung himself from a tree full of white flowers. This tree felt so ashamed that it reddened. Hence it is called judas-tree. It also is said that the Byzantines recaptured Constantinople from Latin invaders when the judas-trees were blossoming, and so value this color.

Do religions have colors? Yes and no. Muslims favor green, as the covers of tombs and sarcophagus are green, and green is common in mosque decorations. Otherwise, Islam does not have its own color. Perhaps people associate green with Islam because Prophet Muhammad liked green, as it relaxes the eyes and connotes nature. In fact, he advised people to dress in plain and clean color-compliant clothes that would please the eyes.

Eastern Orthodox priests dress totally in black and wear a black cap. But this is probably not a religious color, for black is favored by Catholic priests and nuns as well, maybe for its simplicity and sobriety. Some Protestant (e.g., Lutheran) priests wear white or gray, which might be a reaction to the Catholic Church. Also, many Orthodox Jewish sect members wear long black coats and hats, usually during religious or important events to signify the occasion.

Conclusion

Colors are used for many purposes, ranging from medicine to art, politics to anthropology. They are an indispensable ingredient of our lives. But no matter how they are used, the best use of colors is observed in the works of the Great Artist.

Footnotes

1. The Black Hand is associated with two groups: immigrant Sicilian and Italian extortion rackets in America’s Italian communities (roughly between 1890 to 1920), and a secret Serbian terrorist society that promoted the liberation of Serbs outside Serbia from Habsburg or Ottoman rule.
2. Karbala’: A place in southern Iraq where Imam Husayn’s forces were defeated and killed by the Umayyad caliph Yazid I in 680.

References

• Akagunduz, Ulku Ozel. Freedom to Colors.
• Zaman North America 267 (8 Nov. 1999).
• Soylemez, Hasim. Diseases Are Treated by Colors. Aksiyon 242 (24-30 June 1999).
• Sahin, M. A. Truth through Colors (Izmir: 1992).
• www.britannica.com/bcom/eb/.
• www.m-w.com/cgi-bin/dictionary (especially the shades of meaning for different colors).

Travel here and there seeking the seas they parted from.

They fall with the sound of plucked lute-strings;

And hearing it, the earth begins to breathe.

Drops of rain float down with the grace of butterflies,

As if arranging some meaning in most rhythmic verse.

They resonate in the ear like a sweet melody,

And skies seem to weep for the grass on earth.

Each drop has said farewell to its heavenly life,

And returns to its origin, which is a roaring ocean.

Everything on earth holds still to listen to rain;

Each drop descends to the ground like an angel.

Eyes seeing the rain fall in such thrilling harmony

See worlds beyond this world come into view.

The skies rejoice with smiles observed everywhere;

Everyone is enchanted by the heavenly rhapsody.

Vapour rises in masses as great as mountains,

Then it seeks the green, blue and orange on earth.

Rain always brings down a peculiar contentment;

And carries fragrance of Paradise and exhilaration.

That fragrance pervades everywhere, deep into the soul,

Earth awakens to life and flowers burst open.

The whole of creation finds peace and serenity,

The window open to the realms beyond becomes visible.

***