The beauty of the vast blue ocean

I love the ocean. I love its vastness, it lovely hue, the never ending waves, the lovely breeze that comes along with it.. I love it all. Close your eyes and imagine this scenario.. (oopsie.. don't close your eyes as yet .. wait till you get to read the scenario) A dark night, not many stars around, not because the sky is cloudy, but because it's a full moon day and the sheer brightness of the moon is shadowing the brightness of the stars. You are sitting on the beach (facing the sea), legs stretched out, relaxedly, one hand holding your beloved's and the other playing randomly with the sand, while your eyes are mesmerized at the beautiful image of the full moon on the soothing sea.. my my .. what a lovely scene.. brimming with love and happiness. That's how beautiful the sea is..

My son studies in one of the best schools I've ever seen. Best in their approach to education. They believe in raising children to be good citizens along with educating them with the help of a well chosen curriculum. As a part of their homework, they were supposed to pick a heritage/landmark of the city, visit it, list three things good about, list anything they didn't like about it and illustrate their vision of bettering the place. Like you must have guessed by now, we went to the beach. The first thing my son said he liked about it was the blue water and its vastness.

By now, I'm tuned to his thinking and I know what would come next. "Ma, why is it blue". Luckily, this time he was so preoccupied with his pails of wet sand and his sand castles that maybe he put away that question for now. Heaving a big sigh of relief, I googled at once to prepare myself for the imminent debacle. (Oh, by now I include the google brothers in my daily prayers, where I ask the God almighty to bless them with a long long life for having helped me and the many other parents-with-well-inquisitive-children)

What most of us think as the answer to this question, is, "It reflects the color of the sky". If that be the case, then the ocean must be red and orange during sunrise and sunset, grey when it is cloudy. We should be seeing white patches from the white clouds all over the sea. I don't think that is. So, something else must be at play here.

Using the well acquired knowledge from the previous post, one could say, water absorbs all the colours of the sunlight except blue and reflects only blue. Sounds good enough. If that be the case, why isn't the water in a bucket, collected from the sea, blue? Why is it colourless? Or for that matter, why is the water in a glass colourless? What exactly is happening out here?

Apparently, pure water lets out a slight blue colour. ( absorbs all other colours and let's out a faint blue) But, inorder to be able to see that colour, you need a water column of atleast 1 m length. Which is why huge bodies of water are blue, wherein the water in a glass isn't. And when I read further, I learnt that the colour reflected is not due the vibrations of the electrons, like we learnt in the last post, but vibrations of the bond between oxygen and hydrogen. Water is made up of two hydrogen atoms sharing an oxygen atom. Thereby resulting in two hydrogen-oxygen bonds.Apparently, it's the vibration of these bonds that result in the light blue hue which goes undetectable in small quantities.

While that's the explanation, I kept it small and simple with my son. I told him glass of water just lets out small amount of blue, and when there is a huge amount of water, the little blue lights all add up together to make the mighty blue. He gave me the 'aaha' smile and I gave myself a pat on the shoulder.

In my early school days, the most repeated diagram involving the sea was the water cycle diagram. Remember? Water evaporates from the sea. Water vapour being warm rises up. ( denoted by red upward arrows) And as it rises up, it gets colder and forms rain clouds. When the rain clouds have collected enough water vapour, they pour it out as rain.. and the cycle continues. Water changes from liquid to gas state at 100C and we call it the boilling point of water. And any sane person knows not to put his/her hand in the water when it is boiling to avoid scalding. But still, we touch the water in the sea, and it isn't hot. So how does  water change its state? How does the water cycle work? What went amiss?

The process of converting water from liquid state to vapor state is called vaporization. And vaporization happens in two ways. Evaporation and boiling. What happens in the water cycle is called evaporation and it happens at normal temperature. What happens when we boil water on a stove top while seeing lots of bubbles and 100C is boiling of water. Another important difference being while boiling, the entire liquid, that is, even the bottom layers get the energy to change phase to water vapor,which is why you see bubbles rising from the bottom of the pan. Wherein, during evaporation only the top layer changes phase.

You know water is h20 ( read it as ehhch-two-oh ), meaning two hydrogen atoms attached to an oxygen atom. Water has something called intermolecular hydrogen bonding, as in, bonds between two molecules of water. What happens is oxygen of molecule_one of water, bonds itself with two hydrogen atoms of other molecules. The hydrogen atoms of molecule_one bonds itself with one two other oxygen atoms. Thereby resulting in one water molecule being attached through hydrogen bonds with 4 other water molecules ( oxygen1 attached to hydrogen2 and hydrogen3 and hydrogen1 attached to oxygen4 and the other hydrogen1 attached to oxygen5) Lot of bonds right? So, in order to be able to convert phase and enter into gaseous state, these hydrogen bonds must be broken. That's a whole lot of work, meaning a whole lot of energy required to break so many bonds.... Which is why the boiling point of water is high. However, at normal temperature, a little heat is all that is required to break the hydrogen bonds at the surface of the water (sea in our case) to let them escape into the air, thereby beginning the water cycle.

That's why though the sea is not boiling hot, water at the top layer converts to water vapor and brings

us rain eventually. That's settled. Talking of water, and it's change of state, do you know why ice floats on water? Why is it less dense? The credit goes the intermolecular hydrogen bonds again. While in liquid form, the molecules have energy enough to move and slide across one another, where one hydrogen bond is broken while the other is made, enabling free flow. However, when it begins to freeze. the energy is lost and the molecules lose free movement. Hence, the molecules decide that they have to optimally arrange themselves into a convenient form once and for all. We know the hydrogen bonds cause each water molecule to be attached to 4 other water molecules. So, while freezing up, these molecules arrange themselves to form a tetrahedral structure such that the molecules are conveniently far from each other ( so that the like-charged-oxygens are far from each other .. cause like charges repel) Thus, they are placed farther apart than they would be in liquid water. Hence the less density. Hence the floating.

Ice is colourless right? Who knows why the snow is white? Actually, if you look at ice closely, you will find it murky.. You wont be able to see through it, however it would give you a hazy view of the other end. What happens here is that the ice bends the light that it transmits. Hence ice appears transparent , but murky. Now snow is made up of tiny tiny particles of ice. So when llight passes through one particle of ice, the light that comes out is bent and when it enters the next ice particle, bent a little further.. as so on... that finally the light is all bent back at us.. thus reflecting it back at our eye giving us the feel of white. Tadaaaa..

Wow, we've learnt so much today. Isn't it? I started the post with an account of how romantic the sea could be.. Then we learnt somethings related to water, to the sea. I have to mention this one other thing. From when I was a kid, I loved the beach, the sea and the waves. Beach was my favourite go to place. One day, (I distinctly remember,) I fought with my best friend, and I was soo upset. My mom was worried about me and with the intent to cheer me up, took me to the beach. I sat quietly on the sand and was staring into the sea. I watched the waves go back and forth and started wondering why the waves went back and forth. What did they take from the shore, and why they left it at the centre of the ocean and came back. And suddenly, I heard a voice in my head," it is taking your sorrows away little one and leaving it far away from you". I felt a surge of energy first, then my heart felt light, my smile returned, and my mom heaved a sigh of relief.  From that day, till today, I go to the beach whenever I feel the slightest disturbance. And the sea hasn't failed me since. That, I feel, is the real beauty of the vast blue sea..

Why is the sky blue... et al.

We all know the sky is blue. It is pretty obvious isn't it? But three days back, when my son added a 'why' to that pretty obvious statement, and looked at me with big curious eyes, I realized that I didn't know the answer to a question about something that has been over my head all my life. How ignorant could I  have been!! The conversation went like this ..

My 5 year old son : Ma, today it's so hot. See how blueeee the sky is. But ma, why is it blue?
I : It's blue because... because.... ( oh dear, I don't know.. why don't I know... and as an attempt to save face I end up saying ) .... hmm .... baby, what did you learn in school today. Tell me, what did dhiya and prithvi tell you today?
Son : Ma, school was fine. My friends are good. Will you look it up on 'gggooogle' and tell me later?
I :  .....

And the very second I got some free time, I picked up my phone and 'googled' - "why is the sky blue" ... And I read extensively.  One thing led to another and I learnt a lot of fascinating things. ( Don't worry, I think i'll split all the fascinating things into two posts) 

Before we even get on to the why is the sky blue , let's think on this first :  What governs an object's colour ? What if someone asked you,  "Why is a banana yellow?", what would you say? Take a break now, compose your answer and then read ahead. The best answer I could've come up with would've been ,"because.. its skin has yellow pigment". That's all. But, what is that yellow pigment? Why certain pigments and dyes give off certain colour. I drew a blank.

Time to put on our thinking hats (I was tempted to say sorting hats, coz it's the Harry Potter season.. But hey, let's focus ). Keeping the color aside for a moment, what do we need inorder to see things ? We need light to fall on the object and illumiate it. We need an eye to interpret the light that reaches it after illuminating the object. And goes without saying, (as the eye is doing the interpretation), the light has to be in the visible range of the spectrum. So when visible light falls on the banana, and reflects off it and reaches my eye, my eye sees an image of the banana and projects it to the brain. 

And right in between those sequence of events, ( after the light reaches the banana,)  the banana absorbs all the colors of visible light except yellow, thereby reflecting off yellow light, that alone reaches the eye. The brain with the help of the eye, interprets the colour to be yellow. Hence, the yellow banana. Which inevitably brings us to the next question. Why does banana reflect yellow and absorb every other colour? ( when will these nested why questions end? This is how it must feel inside my son's head)

Rather, why do certain objects absorb certain colors and reflect certain other colors. When light falls on an object, the light is either absorbed, reflected or transmitted through. Who or what do you think decides the fate of the incident light? It is the atoms or molecules that make up the object.

Objects are made up different types of molecules and molecules maybe made up of different types of atoms. Atoms could be further broken down into protons electrons and neutrons . Our focus now being on the electrons which are not so tightly bound to be nucleus. Let's say it's like binding a ball to a point with a spring. So the electrons can move up and down. And electrons tend to have their natural frequency of vibration. This natural frequency is the signature of the electrons in the particular type of atom. 

Now each colour from the visible spectrum has a frequency of its own. If the frequency of the colour matches with the frequency of vibration of the electrons in that particular object, that excites the electron and sets it vibrating. As it moves , it collides with the other atoms and the energy is converted into heat/thermal energy. No light comes out. So we could say that particular colour was absorbed by the object.

If the incident coloured light's frequency doesn't match the natural vibrating frequency of the electrons, the electrons don't vibrate for long, but vibrate for a brief period and sometimes transmit the vibration to the neighbouring electrons. The vibration is passed along, and if this goes on, the light is transmitted out at the other end of the object.

However, sometimes, the energy is so insufficient that the electrons on the surface of the object vibrate for a brief period of time and re-emit the energy out of the surface, causing reflection. 

And because every type of an electron and hence an atom has an inherent frequency of vibration, it behaves uniquely when visible light falls on it. Some of them reflect and transmit certain colour lights. Would that imply, that we are equipped to answer the 'what is a pigment' question now? Yes, of course.  Pigment is a chemical that is capable of absorbing some colors and reflecting one or more of the colors in order to lend a certain shade to a certain object. Voila. Neat isn't it !

Back to the banana... Looks like the atoms in the banana absorb every other colour and reflect only yellow. Hence the colour. If all colours would've been absorbed, it would appear black. If all colours were transmitted, it would be transparent. If all the colours were reflected, it would appear white. Get the hang of it?

Wwooh... What a long piece of text before getting to 'the' question : why is the sky blue? Imagining sky as an object and extrapolating from what we've just learnt so far, you would be tempted to say, the atoms in the atmosphere absorb every other colour except blue. Hence the color blue. Right ? Actually, it's a bit more complicated than that.. Don't fret. The knowledge you have just acquired after reading so far is not wrong.( I agree, it sure is hard work. ) Just that it is a different story when it comes to the color of the sky. 

What should we know to be able to understand this story? One, the visible light is made of 7 colors and that each of that color has a wavelength of its own. (violet to red, in ascending order of wavelength) Two, the earth's atmosphere is made up of nitrogen and oxygen molecules, molecules which are very small. Both those sound trivial isn't it ( like my son puts it : easy peasy lemon squeezy ) 

When the light enters the atmosphere, all the other colors travel unhindered, however blue light which has small wavelength is scattered by the  small oxygen-and-nitrogen-molecules. The scattered blue light when it reaches the eye, lends the blue color to the sky. There we go !!!. (Save the question that might be bothering you now, for just a little while longer ) 

That explains the blue sky during the day. However, during Sunrise and sunset, the sky gets a nice red-orange tinge. How is that possible now? What happens to blue light then? During the sunrise or the sunset, the sun is far away from the earth ( as compared to where the sun is during the day) . So the light of the sun gets to travel longer and while doing so all the blue light is totally scattered and the remaining red and orange reach our eyes giving us the wonderful red hue.

Ding dong!! Time for the saved question. If the nitrogen and oxygen molecules affect only the low wavelengths , then what about violet ? Why isn't our sky violet or even blue-ish violet or violet-ish blue? Violet has an even smaller wavelength. Right ? Puzzling!! There's a two part answer to this question. I saw a very colorful graph while investigating this over the Internet about the proportion of the colors in the sun's light. Graphs rattle me a bit, so I'm going to leave it out of here. All it said was, there is less violet than blue in the light that comes from the sun. That's reason one. Reason two revolves around how our eye perceives colour. Apparently, our eye is more sensitive to blue than violet. 

The Retina in our eye has cells called cones that perceive color. And we have three types of cones, blue, green and red which are most sensitive to blue, green and red respectively. However each cone responds to a range of wavelengths. Again, there was a graph to explain that .. I'm skipping the graph. All you need to know is, the violet and indigo lights excite the blue and a little bit of red cones too. The blue light excites the blue as well and little of green cones too. So, when we look up at the sky, lot of blue cones get stimulated, some of green and some of red get simulated. Giving you the combination of blue and little white, the sky blue . Tadaaa!!! ( some red and some green and some blue, gives some white )

So, if the blue color of the sky is perceived in our eyes, it could very well mean that the animals and birds with a different eye structure could see the sky in a different color. How cool is that? A whole new different world out there for them. To support that theory, Did you know that when a honey bee looks at a flower, it can see something called nectar guide. That is, the portion of the flower that contains the nectar shows up highlighted. And that's because the honey bees can see ultraviolet. Buzzing brilliant I would say!! The beautiful ways of nature. 

From why is the sky blue, we have travelled a long way and reached a crossroad called "Is it really blue?". Well, you know what they say ," Color lies in the eye of the beholder".