A CBT PUBLICATION

Neeraja Raghavan

By Neeraja Raghavan

Illustrated by Subir Roy

Children's Book Trust, New Delhi

EDITED BY GEETA MENON AND SEEMA SINHA

Text typeset in 13/16 pt. Garamond

© by CBT 2004 Reprinted 2005

ISBN 81-7011-937-5

Published by Children's Book Trust, Nehru House, 4 Bahadur Shah Zafar Marg, New Delhi-110002 and printed at its Indraprastha Press. Ph: 23316970-74 Fax: 23721090 e-mail: cbtnd@vsnl.com Website: www.childrensbooktrust.com

CONTENTS

What Is Everything Made Up Of? Nothing! 9

^Hello, Who Is Speaking?' 12

I^om Green To Red 15

A Super Factory: The Green Leaf 17

How Tall Will I Be? 19

Water, A Unique Liquid 22

Milky White And Rose Red 25

Twinkle, Twinkle, Little Star 28

What Is That I See Before Me? 32

Strange Turns Of Tops 36

How Can We Hear Ourselves? 40

The Friendly Microbes 43

Changing Face Of The Moon 46

It Is Time To Sleep 49

Instinctive Action 52

'It Gets On My Nerves!' 55

Oh, I Feel So Ticklish! 58

Laughter And Tears 60

Of Soaps And Suds 63

Will My Hair Turn Grey? 66

Whence Comes This Hail? 68

Care For A Cup Of Tea? 71 V

Hie, Hie, Hie! 74

LejjfLeft, Left-Right-Left! 76

Life In The High Seas 78

Scratch, Scratch! 82

Smiling Babies 84

N Barks In Uniform 86

I Wonder Why

I wonder why the sky is blue I wonder how I can see you, How I wish I really knew What, how, where and who?

I set out to ask and get a reply How I looked and how I tried To find out all the reasons why We sometimes laugh and sometimes cry!

You see because I had to know About the sun and the moon And why they glow, And what makes the nails on my toes Grow at a pace that seems so slow.

I couldn't get all the answers fast, In fact, I struggled until the last. Many days and weeks went past Until I met someone at last!

He was tall and old with a balding head And he smiled and looked at me and said: 'My child, come, stop, sit by my side For all you seek is right ahead!'

At first, I knew not what he meant, So I gazed with my head slightly bent, At the grand sphinx-like monument, Which was looking down at us, silent.

Up above the bedpost, carved In shining teak, firm and hard, A sphinx-like face of ancient art Gleamed down at us of curious heart.

Spoke the carved icon of golden mane: 'It is well true that time and again, Many have asked, though never in vain The questions you will ask again.

7 will tell you whatever I know, You must hear me out before you go, For my answers to you will only show, What little we know and what don't we know.

And so, dear friends, this is my tale, Of many a night that the sphinx did regale My old friend and me with a long, long trail Of answers for our 'questions-tail'!

You, too, can come and join him and me, For as the sphinx said, you too, must be One of those who along with me Will sometime wonder curiously!

Remember, though, one serious thing, The world is full of strange happenings, For some we know the reasoning, But for most we are still wondering!

'What makes up this world?' I did ask, The sphinx gave a hearty laugh;

You will soon know the reason why I smile: now hear my reply!

What Is Everything Made Up Of? Nothing!

Anything that occupies space is called matter, whether it is solid, liquid or gas. People have always wondered what matter is made up of. Millions of years ago, they thought that everything was made up of water. There were some who thought everything was made up of air.

Lewis Carroll said that girls are made up of, 'sugar and spice and all that is nice'. And that boys are made up of, 'slugs and snails and puppy dog's tail'! But what are slugs, snails, sugar and spice made up of? Do you know?

A long time ago (in the fourth century B.C.) , a Greek scientist, called Democritus, had an idea that everything in this universe is made up of tiny particles, called atoms (which means something that cannot be divided or cut). Hundreds of years later, a young man, called Dalton propounded the atomic theory.

Dalton's theory suggests that all matter is made up of building blocks, very much like a building is made up of bricks. These building blocks are tiny particles called atoms, which we cannot

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see with our eyes. 'If we cannot see them, can we find out how they look?' asked another English scientist, Rutherford. In 1909, Rutherford conducted a simple experiment to learn more about the structure of the atom. We can get some idea about his experiment with the help of a simple example.

Suppose you have to find out whether a closed box contains air or water without opening it and looking inside. What will you do? A simple way will be to knock at its sides and listen carefully to the sound. A hollow sound will be heard if it contains air, and a heavy sound if it has water. Likewise, Rutherford learnt about

what thin gold sheets are made up of, without actually cutting them up and looking inside. He found that even though atoms make up the gold sheet, within each atom, there is a plenty of empty space.

The rest of the space within an atom is made up of a heavy nucleus in the centre, and there are light electrons which move about the centre.

Scientists have, since the time of Rutherford, learnt still more about the structure of atoms.

In essence, Rutherford was right. Whether slugs, or snails or sugar or spice, all matter consists of atoms which, in their turn, are made up largely of empty space!

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I hardly heard the sphinx tell me these things When all of a sudden the phone did ring,

I finished talking in an impatient tone, Then asked the sphinx: 'Who made the phone?'

'Hello, Who Is Speaking?'

An American, Alexander Graham Bell, built the first crude telephone in 1876. Today, this is the most common means of communication.

Energy is something without which no work can be done. There are so many different forms of energy, some of which you may already know; such as light, heat, sound, electricity, magnetism and many others. Energy as a whole cannot be created or destroyed; what we can do is to change one form of energy into another. What this means is that light energy can be changed into heat energy, electrical into magnetic, sound into electrical, and so on. Just as sound energy can travel through air in the form of vibrations or sound waves, if we convert the sound energy into electrical energy, we can make it flow through wires!

The basic principle of the functioning of a telephone is that of

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inter-conversion of different forms of energy. This is exactly what Alexander Graham Bell succeeded in doing.

It will be easy to understand the way a telephone works if you picture a 'relay race' taking place from the mouthpiece of the speaker's telephone to the earpiece of the receiver's telephone. In a relay race, one runner runs up to another person standing far off, and gives him/her an object. In turn, the second person runs and again gives the object to a third person, and so on, until the end of the race.

When we speak into the mouthpiece of a telephone, the sound waves that come out of our mouth make a thin metal sheet inside the mouthpiece vibrate, that is, move back and forth. Packed loosely behind that sheet are small carbon pieces, which feel the vibration of the sheet, and become more or less tightly packed,

depending upon the way in which the sheet pushes them. This, in turn, changes the amount of electric current that passes through them. Sound waves are changed into electric waves. It is exactly as if the first 'runner' has given the packet of sound energy to the second 'runner', who has taken the packet in the form of electrical energy while running. These electric waves travel through the wires from the mouthpiece of the speaker to the receiver of the listener. In the earpiece, the opposite conversion takes place, that is, from electrical energy to sound energy. This happens in the reverse order. It is, as if the third 'runner' converts the packet of electrical energy into magnetic, while the fourth 'runner' changes the packet into sound energy from magnetic energy.

After the long relay race (which takes so little time that we do not even know it is happening), we are able to hear the same words as spoken by the speaker at the other end of the line!

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'Which means,' I said, 'that all are same, Made up of nothing, but differ only in name,

I call this heat, that looks like light, In actual fact, they are all energy bright.

Tell me, sphinx, if that is so, How do the fruits and vegetables know

When to turn deep red from green, And when to brighten up the scene ?'

From Green To Red

No, we are not talking of the traffic signal! Have you ever wondered how a basketful of green tomatoes slowly become red ones? What makes a raw tomato or an apple green, and a ripe one red? What is the cause of this magical colour change?

Just as certain colours dye the clothes you wear, plants have pigments in them that are responsible for their colour. Green plants have a pigment, called chlorophyll, that has the property of allowing the plant to trap light energy and use it to make its own food. Green plants do not need to be fed with anything except water, fresh air and sunlight. Once they get these, they get busy making their own food. There are other kinds of pigments too, and these occur in different parts of the fruit in different degrees. There are less of the carotenoid pigments in the pulp of a fruit than in the peel. Does that name sound tough for you to

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pronounce? Of course, not! You do like carrots, don't you? At least their bright colour? Well, the molecules that are responsible for the colour of carrots are called caro-teen-oyds—carotenoids, a class of compounds that catch light and respond to it by showing a characteristic colour. Carotenoids occur in the peel of an orange, as well as in the peel of an apple. Lycopene is the name of the main red pigment in tomatoes. (There are many coloured molecules; you are just reading about a few here.)

When a tomato ripens, two things happen. The amount of green pigment (chlorophyll) slowly decreases and the amount of red pigment {lycopene and some carotenoids) slowly increases. Have you seen your mother leaving tomatoes sometimes to ripen in the kitchen cupboard? Well, that is because the formation of the red carotenoids does not require light. In fact, the fruit does not need to remain on the vine to ripen, for raw tomatoes can be plucked off the vine and then left to ripen in storage. Scientists are sure that the switch which starts off the formation of the red carotenoids in tomatoes is not light. They are trying to find out what it is!

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7 am hungry, sphinx,' I said, with a sigh, And ran off, saying, 'See you later, bye.' When we met again, after my tasty treat,

My next query was: 'How do the plants eat?'

A Super Factory: The Green Leaf

All our industries cannot match the simple green leaf. FoT industries can only try to reach a high efficiency, limited by many factors. Leaves, however, quietly produce things that we cannot see with our eyes, but can sense in other ways. And they do it with a hundred per cent efficiency.

Do you understand what this means? All the raw materials in a factory cannot get converted into the final product; some will remain but raw materials. Add to this the fact that machines cannot operate with perfect efficiency, nor can human beings who work in a factory, and you have a good set of reasons why industrial production can never be a hundred per cent.

The quiet little green leaf has within it a highly efficient factory, which operates with a hundred per cent efficiency. Do you know

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why? Inside a blade of grass or a green leaf, there is the pigment, chlorophyll. This and other molecules inside the plant succeed in producing from water, air and a few metals and minerals from the soil, substances as varied as the scent of a rose, the opium of poppy, the dye of indigo and many other things.

We know that the green globules, chloroplasts, impart colour to the leaf, and have the power to absorb light energy, which is transformed into another form of energy, about which we know little! This energy is able to split water into hydrogen and oxygen, something we can do with great difficulty in the laboratory. Then starts a long series of reactions which, for example in a rose bush, is responsible for the colour of the rose and for its scent. Chloroplasts on their own can manufacture starch and sugar. The mystery is obviously hidden in these chloroplasts.

If you realize how slowly and unwillingly the leaf revealed a few of its secrets to some of the greatest minds, you can understand what we mean when we say that our laboratories and factories are a long way behind the green leaf!

'Why is it, sphinx, that I don't grow So tall that the birds will know As the one above the tree top,

One who grows without a stop ?'

How Tall Will I Be?

I am sure you have asked that question many times. If you are among the tallest in your class, perhaps you wish you were not. And if you are not tall enough, I will bet you wonder whether you will grow tall really fast!

Why is it that we can grow fatter as we age, but we cannot simply become taller and taller? You may have seen your aunts and uncles grow fatter even as they get older, but have you ever seen them grow taller all the time? Why not?

Do you know that your body is made up of more than ten million cells? As each cell grows bigger and bigger, there comes a stage when one big cell divides and becomes two, two cells divide and become four. This goes on and on inside you, and inside everyone. As you grow, your muscles and bones develop more and more cells inside them, which is why children keep hearing, "Drink your milk, it helps you to grow!"

Fat cells are different from growth cells. Depending upon the type of food that we eat, and the kind of exercise that we do, the fat cells add themselves to the existing cells. There is no limit to the amount of fat cells that we can add, so we can go on getting fatter all through our lives. As the number of cells inside your bones and muscles increase, naturally they get bigger. However,

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this does not mean that you will go on growing and never stop. This is because, as your body makes new cells, old cells wear out. Another and more important reason is that there are certain organs in your body called glands. There are tear glands, sweat glands, oil glands, glands that help you digest your food, glands that help your heart to beat faster, glands that help you grow and so on. One such gland, called the pituitary gland, is like the captain of a ship. This fellow controls all the other glands, and orders them, 'Hey, guys! You must all work together!' Along will come a day when this smart gland, the pituitary gland, will tell all the other glands, 'You know, I think it is time you folks stopped. Just take it easy. This body has grown enough for now.' And by then, you will be somewhere between sixteen and twenty-three years old. By which time your legs will be about five times as long as they were when you were a baby, your arms will be about four times as long, and your head will be about twice as big. Surely, that is enough? Well, whatever you may think, your pituitary gland certainly thinks so!

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'Have you ever noticed one thing?' Asked the wise old sphinx, gently smiling,

'We drink a liquid everyday, Which we can keep in any which way.'

Water, A Unique Liquid

Do you know that more than seventy per cent of the world is made up of water? The commonest liquid on earth, and yet the strangest in many ways. Do you ask why we call it strange? Have you noticed that water has no shape of its own? No colour, no smell, no taste. Pour it into a glass and it takes the shape of the glass; what is more, you can see right through the glass of water. On a cold day, oooh! It is so-o-cold! And on a hot day...why, there it goes again! Does this water have no character of its own? It feels cold if the day is cold, and hot if the day is hot! In a cup, it looks like a cup, and in a botde, like a bottle! With sugar,

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it tastes sweet, and with salt it tastes salty. Here is a copycat if ever there was one!

In fact, all the while, water is really very unique. It simply pretends to be a copycat. You have seen how water is wet, have you not? I mean, you cannot dip your hand in water and lift it out dry. Why is that? It is because water, like anything else, is made up of molecules. Water molecules tend to stick together. They hold onto each other like real buddies. They would not even let go of each other when any other object comes in contact with them, like say, a glass, or a cup or even your hand. A bunch of water molecules gang up and touch the object, making it wet. Like most liquids, the molecules in water are not as tighdy held together as in solids. Take the book you are reading now, for instance. It has a definite shape, and is a solid. It is made up of molecules that are so tightly packed that they do not move about as freely as water molecules do. This explains why water takes up the shape of the container it is poured into. Air is made up of

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molecules that are so loosely packed that they spread all over the place available to them. Gases cannot be kept tightly shut unless a lot of pressure is applied to the container they are held in. The gas molecules are dancing about so fast that they cannot wait to jump out into any inch of available space!

Water, you must have heard is said, will find its own level. This means when water is poured into columns or tubes, it will fill those tubes only upto a point, that is, the original level of liquid from which it is poured. The height of this point is determined by the force felt by the water due to the air above it, called the atmospheric pressure. It also depends upon the energy that is contained within the water to stretch itself out, called the surface tension. It makes sense, doesn't it? If you wanted to spread yourself out, how far you could do so would depend upon two things—your own strength and that of those around you. Which is the reason why the water that rises up a pipe can do so only upto a certain point.

This means that water is neither too rigid nor too loose. Unlike most liquids, it has no colour, taste or smell. These properties are because of the elements hydrogen and oxygen, that form water. These two elements react to produce a highly stable substance. What does 'stable' mean? It means that water is so happy being as it is, it does not need to change in any way. It is content to keep flowing in the river, or tossing about in the ocean, or sitting still in the lake. It absorbs no light, so it has no colour. It has no gases to let off (unless it is fouled up), so it has no smell. Since it hardly reacts with anything, it cannot produce a smell unless the substance that we put into it has a smell.

Water is a wonderful thing. How many of us can be like it? Adjusting, flowing, free, mobile, hardly noticeable and yet very, very useful!

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The world is full of colours bright, Some deep red and others just white,

What is it that tells each thing to show, Just that colour and just that glow ?

Milky White And Rose Red

Have you ever wondered why milk is white? And a rose is red?

Would it not be funny if milk was red and all roses were white? Colour is so typical of everything, that we often call a colour by an object that we have seen in that shade.

What makes anything coloured? There are so many differently coloured objects, but all of them

appear the way they do for the same reason. Light that falls on the object bounces off it and reaches our eyes, where we 'see' the colour. In fact, the ordinary light is not ordinary at all, as demonstrated by Isaac Newton almost three hundred years ago.

An 'ordinary' ray of light is made up of seven colours, which are the colours of the rainbow. They are: violet, indigo, blue, green, yellow, orange and red.^i^hen a beam of light passes through droplets of water, it splits up into its seven colours, and we see a rainbow in the sky. Further, Isaac Newton showed that when these seven colours mix together, they form the white colour. Have you ever tried painting a colour-wheel with bands of the seven colours? When this wheel rotates very fast, you will be able to see greyish-white as a result.

Is it not strange that light appears to be just a simple ray, although it is actually made up of so many colours? Whether we see the seven colours or not, these colours strike any object whenever light falls on it. Each time these colours hit an object, the particular object selects the colours that it can absorb, and allows the others simply to bounce off its surface. For instance,

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a green leaf is green because the leaf absorbs all colours except green, and it is the green colour which reaches our eyes. So we see the leaf as green. A red rose, similarly, allows only red to reach our eyes and absorbs all the other colours. A white substance, or milk, absorbs none of the colours but reflects the whole band of seven colours. When these seven colours mix, they appear as white. A black object absorbs all the colours, so we do not get any light from it falling on our eyes, and we see it as a dark and black object.

You may well ask why does a leaf not absorb green, or milk does not absorb any colours at all? It all depends on what a leaf, or milk is made up of. There are pigment molecules inside a leaf, chlorophylls, which are the cause of a leaf's green colour. There are no pigment molecules in milk, so it does not absorb any light at all.

Finally, that is what it all boils down to. What each thing is made up of, and the nature of the molecules that make up an object decide its colour. Why are you fair-skinned and your brother dark, is because of the pigments in your bodies!

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By this time it was well into the night, And as we sat, in starlight bright, My old friend asked me if I knew

Why stars twinkle. 7 don't, do you?'

Twinkle, Twinkle, Little Star

On a clear night, have you watched the stars? Twinkling away quietly, like a million diamonds in the sky, they make you feel there is some movement of these bright bodies so far away from the earth. In fact, as you may know, stars are shining bodies that give out their own light and it is the earth which moves around one such star, the sun. Why then, do stars look like they are moving ever so slighdy? Have you noticed another aspect? Only the sun looks like a big ball, all the other stars look like pinpoints of light, somewhat star-shaped. Why is that so?

A star is a huge ball of glowing gas in the sky. What makes it

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glow? There are mainly two gases in a star—hydrogen and helium. These two gases give out a very powerful form of energy known as nuclear energy. (It is the stuff that bombs are made of!) It is not surprising that these gases make the star very hot, so that it continues to shine until it runs out of hydrogen. It is rather like an engine running out of fuel, and that is when the star explodes into a huge cloud of gas and dust. Since the sun is the star that lies closest to the earth, we can see it as a ball-shaped object. All the other stars in our galaxy, the Milky Way, are so far away that they appear to us as pinpoints of light, if they can be seen at all by us. Do you know that there are more than 200 billion billion stars? (That number has twenty zeros after 2!)

Stars are of different sizes, colours and brightness. Some are so huge that they would more than fill the space between the earth and the sun. Such stars have a diameter that is about one thousand times as large as the sun's. The smallest stars are smaller than the earth. Though they appear to be very close together,

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stars are actually far apart. The star nearest to the sun is more than 25 million million miles away from the sun.

Some stars are yellow like the sun, while others glow blue or red. The colour of the star will depend upon how hot it is, rather like the colour of glowing ashes changing from white-hot to red-hot to black, as they cool. Have you watched a dying fire's embers change colour? The colour of starlight changes because of changes in energy.

Just as the sun appears to move across the sky during the day

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(but, in fact, it is the earth which is moving), so also the stars appear to move across the sky at night. This movement comes from the spinning of the earth, not from that of the stars. The stars move, but their movement cannot be seen from the earth as they are too far away. Stars twinkle because starlight comes to us through moving layers of air that surround the earth. Have you looked through the smoke that moves above the flame of a candle? If you have, you would have noticed that anything that is seen through the moving smoke appears to be moving, too! Actually, it is the air between our eyes and that object which is moving, so we think the object itself is moving. It is exactly the same thing that happens when we see stars twinkle.

Where do stars go during the day? Nowhere. TRey stay right where they are, only the sunlight is too bright for us to be able to see the stars. Shine a torch inside a room full of bright bulbs, and you would not be able to see the torchlight. Not until you turn all the lights off will the torchlight become visible. So the starlight becomes visible only when the sun is no longer shining bright in the sky.

Do you not think a lot of what we 'see' is not really so? Stars seem to move and twinkle, but actually they do not. Stars seem to disappear during the day, in fact, they do not. Why, our eyes have stories to tell! Not only eyes.. .watch out!

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When we do see with our eyes, A flying saucer in the sky,

Whence came it there, do we know? How does it come, where does it go?

What Is That I See Before Me?

Have you been on the road on a hot, dry day? Did you, by any chance, see a pool of water just up ahead, which disappeared as soon as you came near it? If you did, you are not the only one to have seen such a sight. The sight of a welcome oasis 'just up ahead' has fooled many a weary traveller in the desert.

This is called a mirage. The word comes from a Latin word, mirare meaning 'to look at'. You may look at something which may appear to be there, but no sooner do you get close to it, and poof! It disappears! Does that mean there is some magic going on?

In fact, there is no magic at all. Have you learnt that light travels as rays? And that these rays travel in straight lines? But if the rays move through layers of air that are of different thickness (or density), the speed at which they move through the thinner layer is different from the speed at which they move through the thicker layer. A ray of light bends as it travels from a thinner layer to a thicker layer of air. On a hot and dry day, the hot air near the surface of the road bends (or refracts) light rays from the sky towards our eyes. If we happen to be travelling along the road, we see a part of the sky on the road in front of us. Had it not

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been for the bending of the light rays, we would not have been able to see this! Sometimes, the resulting image includes part of a cloud. So we see what looks like a distant lake. It is not actual, it only appears so.

Can we photograph a mirage? Yes, because light rays make up a mirage, they can be photographed. Trees are sometimes seen upside down, as they look in a pool of water. This is because the

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layers of air of different density bend the light rays—coming down from the treetop—upward again. This happens along our line of vision, and our eyes automatically trace the ray back to a virtual (not real) image, and we actually see the top of the tree which lies beneath the horizon. In fact, it has happened to sailors at sea that they cannot see a distant ship because of hot air layers, but they do 'see' the ship in the sky, upside down!

The ancient people knew about mirages, but the concept remained scientifically unexplained until the late eighteenth century. Gaspard Monge travelled on Napoleon's expedition to Egypt in 1798, and he saw such images. He soon realized that the bending of light waves in the atmosphere caused them.

Today, there are scientists who believe that 'flying saucers' are, in fact, nothing but mirages.

What we are saying is that you may see something which may

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not be real! Like when you see yourself behind the mirror, are you actually there behind the looking glass? How then do you know when to trust your eyes? Think it over.

'Then how on earth will I know,

That what I see is really so, And it isn't just a faint mirage,

Or a bent ray of light looming large?'

'Ah, my child, you ask a very difficult thing,' Said the sphinx, gently smiling,

'For to know and understand reality, It is not enough with the eye alone to see.'

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What makes things move, what makes them stop? What is it that keeps a spinning top

From falling over once it is spun, And why does it fall before a spin is begun?

Strange Turns Of Tops

How things move depends upon a number of things. Most of all, it is important to understand that there are laws which govern the motion of all objects. They may seem just to happen, but in fact, they do not. The two famous scientists, Galileo and Newton, are mainly responsible for discovering the Laws of Motion. Simply put, if an object is left alone, and is not disturbed, it continues to stand still if that is what it was originally doing, and continues to move with a constant speed in the direction in which it was originally moving. That makes sense, does it not? I mean, why on earth should an object that was standing still start

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moving unless it was pushed? And why should a moving object change its speed or direction of movement unless it was disturbed? Galileo called this the Principle of Inertia. Inertia is the name given to the property oFa body to remain in its original state. (You will understand exactly what that means when you are asked to jump out of a comfortable bed to study mathematics. What you experience is a kind of inertia!)

Why, then you may ask, do moving bodies come to a stop even when there is no obvious disturbance to their motion?

For instance, if we slide a block across a table, why does it stop sliding after awhile? This is because the block is not really left to itself, it is, in fact, rubbing against the table. This slows it down and causes it to come to a stop finally. The same is true of a spinning top that slowly comes to a stop, even if we do not touch it. The surface it is resting on, the air around the spinning top, all these are not leaving the top to itself, which is why its motion ceases after awhile.

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I am sure you must have spun a top sometime in your life. It is fun, is it not—to see the little object poised on its sharp point and spinning at a terrific speed without falling over? How does it do that? You know that a top will not stand on its point, but will fall down if we try to rest it on its pointed end. Yet it manages to spin away resting on that very point! Is that not strange? Not really, if only we remember the principle of inertia. Every atom in the top moves in a circular plane, its tip rotates around a line, called axis of rotation. (An example of a plane is the surface of your book; that of a line is a thin piece of string.)

The force of gravity makes a top topple over if we simply try

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to rest it on its tip. (This is the name given to the pull that the earth exerts on every single object, and the pull is greater if the object is more massive.) Once we give it a force, large enough to set it spinning, it continues to spin on its tip, without falling over.

This is because the spinning force we have given it is enough to balance the force of gravity. In fact, the larger and heavier the top, and the faster it is set into a spin, the easier it will be to keep it spinning. Each little atom on the top is moving along with the top, and it would continue its movement in the same direction. If you try to tilt or topple the top by gently pulling it forward, every atom in the top will try to resist this change by continuing its motion in the plane perpendicular to the rotation axis. The axis of rotation also seeks to retain its original direction. In other words, the top continues to spin in the direction that it started to spin, as the law states.

Now along comes your neighbourhood bully, and sticking his tongue out, he pulls the top with such force that wham! It does indeed topple over! How did that happen? Well, he also had to obey a certain law. You see, the bully knew just how much force to apply so as to exceed the force which was keeping the top spinning. Once he did that, the top had no choice but to fall!

'Ah, now I see the law,' I said, 'That lets the top stand on its head. To get something to move from rest,

It needs a force to manifest. '

'That is right, my child,' the sphinx did say, 'And once you have it on its way, Its motion will not simply end,

Till a greater stopping force we send. '

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'When I shout out from a mountain top, Why is it, sphinx, the shout won't stop ?

And if I shout along the plain, Why don't I hear it come back again?'

How Can We Hear Ourselves?

Have you ever heard an echo? Sometimes, if you walked into a large and empty room, and called out your name, you would have experienced your own voice calling out your name back to you! If you have gone to the mountains and shouted out from among many peaks, you would have heard what is termed as an echo. What is an echo? How is it created?

Whenever we hear any sound, it is because the object or person producing the sound has disturbed the air around us. We say that sound waves have been produced; these waves are carried to our

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ears as we hear the sound. You have seen waves in the water, have you not? Such waves are also produced in the invisible air, so we cannot see them. If there is no air, we cannot hear any sound. In the higher peaks, the air is very thin, and often mountaineers can barely hear each other, because not many waves are produced in the absence of air.

The first important condition for any sound to be heard, whether it is an echo or not, is that air or water (called a medium) must be present for the sound waves to travel. For an echo to be produced, there should be something that comes in the way of the sound waves (called an obstacle or barrier). The obstacle should be located at a distance that is quite far from the person shouting. The reason for this is that when you call out your name among the mountain tops, the first sound you hear is due to the sound waves produced immediately near your ear. The second sound (echo) you hear is due to the train of waves that travelled

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all the way to a mountain, hit the side of the mountain, and bounced back to your ears. (This is similar to the reflection of light waves by a barrier.) Since this journey takes some time, the echo is heard but after a gap of a few seconds.

Not all obstacles can cause echoes, however. Some objects absorb the sound instt \d of reflecting it. This means that the sound does not bounce back and there is no echo. Sometimes, you may hear more than one echo. This happens when there are many such barriers, and each barrier sends back the sound waves at different intervals to your ears, depending upon how far away each barrier is from you.

In a small room, the first sound and its echo are so close to each other in time that we hear them together. This means that a non-absorbing barrier always produces an echo, even if the barrier is very close to us, but we can only hear it when we are far away from the barrier.

In fact, scientists use echoes to measure the depth of the ocean. They explode a small bomb at the tip of a ship, so that the sound hits the bottom of the ocean and comes back to the ship. When they measure the time taken for this, they can easily calculate the depth of the ocean by using a simple formula. Clouds reflect sound and cause echo. When we hear the rumbling of thunder, this is the result of the first sharp clap being reflected again and again by the clouds.

There was once a castle in Italy that used to produce thirty echoes for a word said in a loud voice. Do you wish you could take your neighbourhood bully there and call him names? Sorry, it has now been demolished!

When I speak in a very loud tone I may just hear one sound alone, If I wish to hear the hidden echo

Before a reflecting barrier I must go.

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My old friend was feeling low, So to perk his health he had to go To the drug store for a red tonic,

Without which, he said, he felt quite sick.

After that, he didn't look quite so ill With the tonic he had also a pill,

How did the tonic and the pill know What to do and where to go ?

The Friendly Microbes

Have you ever fallen sick and stayed in bed for a few days? Did you have to drink bitter syrup and swallow colourful capsules? I am sure you have tasted such medicines at least once in your life.

Some of these medicines have fancy-sounding names. They are called 'Antibiotics'. When these substances are put into your body, they kill or stop the growth of certain kinds of germs. They help your body fight disease. They are actually made from tiny bacteria and moulds, a form of life called microbes. These

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microbes are able to produce chemicals that kill other disease-causing microbes. Scientists have discovered that there are friendly microbes as well as not so friendly ones. The latter cause diseases, while the former help fight them! The disease-causing germs grow in our bodies by dividing from one germ into two, from two into four, and so on, very rapidly. Soon these germs eat up the food that should normally go towards making the body strong, so the patient feels weak even after eating a meal.

The scientists grow the friendly microbes in the laboratory, collect the chemicals which they produce until they are in large quantities, and then make these chemicals into capsules or pills for you to buy from the local drug store.

How do antibiotics cure diseases? How do they get to the right

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part of the body to work there? Strangely enough, science still does not provide the answer. Some scientists believe that antibiotics work by cutting off the supply of oxygen to the disease-causing germs. Without oxygen, the germs cannot go on dividing, so their number slowly decreases. Another group of scientists believe that an antibiotic works by preventing germs from taking in food from the patient's body so that the germ final ly starves to death. Still another theory is that the germ mistakes the antibiotic for part of its usual diet, eats it and is poisoned.

You must be familiar with another class of tablets called pain-killers. Aspirin is believed to act by stopping the body from making the chemicals that are needed for us to feel pain. Other painkillers act on the central nervous system (also see chapter 'It Gets On My Nerves!' for explanation of how the nervous system works) and make us feel less pain.

It is quite l ikely that one or more of these theories work at any given time and, when we take more than one medicine at a time, each of these probably works in a different way. While one drug may work by kil l ing the germs, another may just weaken the germs so as to allow the body's natural defences to take over. What does 'natural defences' mean? This means the chemicals produced in our body naturally. Some of these may themselves work towards fighting diseases, and when the disease-causing germs are weakened, we may be able to recover from our illness by way of weakening the germs with the help of medicines.

We owe our knowledge of the germ theory of disease to Louis Pasteur, the famous nineteenth century French scientist. Alexander Fleming, the twentieth century discoverer of penicillin, stated, 'Without Pasteur, I would be nothing.'

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The moon is shining with a soft glow, It appears to me almost yellow.

But yesterday it was sparkling bright, How does it change from yellow to white?

Changing Face Of The Moon

Have you noticed how the moon looks a dirty yellow on some days and white on others? Does it mean the moon is changing everyday? What is it about the moon that makes us see a different colour on some days?

The moon shines because of the sunlight that is reflected off its surface. The moon has no light of its own. If we were to stand on the moon, we would see the earth shining because of the sunlight reflected off the earth's surface. In fact, the sunlight reflected from the surface of the earth also bounces off the moon's surface; it is called 'earthshine', because it is sunlight that has travelled to the earth and then reached the moon.

Of all the sunlight that strikes the moon, only seven per cent

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is reflected by it. On the other hand, the earth reflects 36 per cent of the sunlight that falls on its surface. The moon has no atmosphere unlike our earth. When sunlight (which contains all the colours of the rainbow) strikes the moon, we see the colours which are allowed to pass through the earth's atmosphere. It appears silvery-orange to us because the atmosphere of the earth has blocked off the darker light rays reflected from the sun. Astronomers say that the moon is actually dark brown. Brown is the colour of cooled lava and pumice (volcanic glass) which make up the surface of the moon.

As it rises, the moon appears orange because the atmosphere at the horizon is so thick it shuts out the silver rays. There are patches that we can see on the moon, for some areas on the moon are of higher brightness than others. This has a reason, there are slopes and valleys on the moon which cause shadows and some bright spots. During full moon and the days immediately preceding and following it, the sun, earth and moon are in a direct line in that order. The shadows cannot be seen in this period because the sun's rays strike the moon directly. (It is the same reason why your shadow is the shortest at twelve noon, when the sun is directly over your head.) Occasionally, a 'ring around the moon' is caused by the reflection of moonbeams from ice crystals in the upper atmosphere.

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I can tell just from a yawn, It is time to bed I be gone,

But how is it the birds can tell, When to sleep and wake as well?

It Is Time To Sleep

Whatever sleep is for, we cannot do without it. (If you have stayed up late studying for an examination, you will know what I mean, on the next drowsy morning.) Some people have managed to stay awake up to six or seven days without any apparent ill-effects, but in laboratory experiments animals that are not allowed to sleep eventually die. This shows that like food and water, sleep is essential for life to continue among animals and human beings.

What happens to us when we sleep? The brain is far from resting during our sleeping hours. It is highly active, though the nature of activity is different from the kind that goes on during waking hours. In fact, the brain is so important in controlling sleep that it is thought that sleeping only occurs in higher vertebrates with fairly well developed brains. Scientists have studied the changes in the brain when we sleep by noting what are called brain-wave patterns. (This is a pattern which is recorded by certain instruments that are connected to the brain of the sleeping person or an animal.)

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Some scientists believe that sleep is necessary because it is a method of conserving energy. During sleep the muscles relax, the heart rate and respiration slow down, and the body temperature falls. Sleep can help animals avoid extremes of temperature. Birds and animals pass through the same stages of sleep as humans and the same type of brain-wave pattern.

How do we know it is time to sleep? We see the time and we

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know it is bedtime! But what about those who cannot tell the time by looking at a clock, like the birds and animals?

The brain controls the daily 24-hour cycle of sleeping, waking, as also body temperature variation. Both temperature and alertness rise with the morning and fall towards the evening, reaching the lowest point during deep sleep. In the absence of clocks or cues to indicate day and night, human volunteers living alone adopted a 'day' that lasted between 26 to 30 hours, during which they slept up to ten hours and stayed awake up to 20 hours. It is as if there is a biological clock within our bodies, which tells us it is time to sleep even if we do not have any idea of the actual time of the day. This shows that the rising and setting of the sun is one of the reasons why we are so used to a 24,-hour day. If we did not see the rising and setting sun, we would probably also have a 26-to 30-hour 'day'. Blind laboratory animals have been

It is the alternation of daylight and darkness that resets the clock in us to a 24-hour day. Most birds fly only in the daylight and sleep at night. In all cases, their body clocks are matched with the daily routine of day and night. During a total solar eclipse, when there is sudden darkness in the middle of the day, you will notice the birds huddling among the trees, joining their voices in a puzzled twitter. It is one time when their body clocks and the outer clock of daylight are not quite matched! When severe cold threatens a bird or animal, it reduces its energy needs by going in for a long sleep called hibernation. Its heartbeat, metabolism and body temperature are greatly reduced. It is almost as if the bird or animal is 'dead', though actually it is alive. Thus, sleep is the body's way of getting rest, fighting bitter cold and regaining energy.

found to adopt such long 'days'.

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I asked: 'There are some acts that many a time Take place with no reason nor rhyme,

When we see danger, what tells the brain To protect ourselves, time and again?'

«

The sphinx answered: 'In order to survive this life

We need to handle stress and strife, With instincts that help us to face, Many a danger in many a place.'

Instinctive Action

Some actions that we perform are automatic. We do not even have to think about jerking our fingers away when we get an electric shock from the fridge, or a cooler; or pull our hands away from a flame. How is it that certain things do not have to

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be taught to us? What tells the body how to act in such a situation? In the animal world, instinctive action (as it is called) is even

more common. Bees, ants and wasps lead very complicated lives, in which hundreds of thousands of insects live in the same nest and do many different jobs—all quite naturally. We say that these social insects live not by thinking, but by instinct; human beings live partly by thinking and partly by instinct. The latter kind of behaviour requires no learning and is called innate, meaning 'existing at birth'. Usually such behaviour is triggered off by a simple situation, for example, imagine five persons of different ages in a dark room. Suppose suddenly one of them turns on the light. At first everyone blinks. Then their pupils become smaller to protect the eye from excess light. Nobody in*the room has to think about making his or her pupils smaller.

A herring gull that is newly hatched from its shell is drawn like a magnet to the red dot on its parent's bill. The chick pecks on the dot, prompting the parent to spit out a piece of partially digested food into its little mouth. This is instinct. The birds—

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mother and chick, know what to do. It does not matter that the chick has never before seen this behaviour or that its mother has not had a chance to give it a lesson in table manners; every newly-hatched herring gull acts the same way.

We say that such actions are based upon instinct. The truth is we know little about how they happen. We know that instincts are usually related to survival, and that they are programmed into the brain of every creature. Young birds who have never seen a snake, for example, know instinctively to avoid the poisonous reptiles.

The simplest instinctive action is the reflex. Sit on a chair and swing your left leg over the other. Hit the top of your left knee with a light hammer. You will find that your knee jerks out of its own accord. This is an example of a reflex action. Laughter and tears are acts that sometimes take place without a thought. They are reflex actions, though sometimes we can control our laughter and tears.

Nest building, food-gathering, mating, attack and escape movements are all examples of instinctive behaviour. Some of these behaviour patterns are so firmly set, that they are completed even when it is clear that they will fail to produce the desired result. If an egg under incubation by the greying goose is pulled away from under her and removed from her sight, she wil l continue as if she is pushing it into the nest.

There are certain groups of molecules called genes in our bodies and also in animals, that control instinctive behaviour. Changes in these genes can affect the behaviour of the creature. Scientists are still debating how much of animal behaviour is learned and how much is instinctive.

When you smell the cake that is being baked in your mother's kitchen, your mouth starts watering; you do not have to tell it anything! Your instinct is at work.

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When we trip and fall down in pain, There is, in fact, a long, long chain

Of messages sent out from the brain That keep us from falling down again.

'It Gets On My Nerves!'

Have you noticed that a pinprick on our finger hurts as, yet we can cut our fingernails without experiencing any pain? We can cut our hair with the sharpest scissors without feeling any pain at all, but just try to place the edge of those scissors against your head...my! Even the thought hurts, does it not? What causes pain? Why do we feel it in some places and not in others?

In order to feel any sensation, whether pain or pleasure, we must have cells that are alive and connected to nerves. Our fingernails and hair are made up of dead cells and do not possess

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any nerve fibres at all, so it is not surprising that they do not cause us pain or pleasure. Nerves carry the sensation of pain to the brain, and the brain acts somewhat like a complicated computer. The nervous system is made up of billions of cells called neurons or nerve cells. Tied together in cord-like bundles, these nerve fibres (or nerves) act like a bundle of wires that cany information very rapidly throughout the body. (The speed at which signals travel through nerves is simply astounding— a maximum of 300 km per hour, a speed at which even the fastest car cannot travel!) Special neurons are found in the brain and the spinal cord.

You will be able to understand the way our nervous system operates if you remember one simple thing that energy can be changed from one form into another. Light energy can be converted into electricity not only in solar cells, which you may have seen, but also within our own bodies. Nerves carry messages rather like electric wires carry electricity. These electric impulses, as they are called, are nothing but packets of electrical energy. It is these electrical energy packets that make up nerve messages.

Take a simple example. If a person sees a tiger on his path, it will not take him/her long to run for his/her life! The person's reaction may take only an instant, but the reaction actually is the result of many complicated processes within the nervous system. Since these take hardly any time, we seldom think about them. As shown in the illustration, in a stepwise manner, these are the things which occur: • There are special neurons in the eye which translate the light

rays that reflect off the tiger into nerve messages. • These nerve messages travel at a terrific speed through the

neurons to the brain. • The brain receives the messages, understands them, and

suggests the action to be taken. • 'Run!' says the brain, again in the form of nerve messages.

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These nerve messages travel to the neurons located in the muscles of the legs, as a result of which the person runs.

At the same time, the brain sends out messages to other parts of the body, for example, 'Look here, heart! You must beat faster so as to send more blood to the leg muscles, as they need it!'

Since these steps happen so very fast, we are on our feet before we know it!

Even the most advanced computer made by man cannot match the human brain in its speed and complexity. This is the reason why the brain is so important for proper functioning of the body. If we feel pain and the nerves in the brain do not tell our body what to do, can you imagine the dreadful result? We are lucky indeed to have a terrific computer inside us!

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'Now I know about nerves,' I said. 'They get orders from inside my head.

If they take back signals from outside, Why do I laugh when you tickle my side ?'

Oh, i Feel So Ticklish!

The best way to make a serious person laugh is to tickle him or her! In no time, you will have the person burst out into loud laughter. The famous scientist, Charles Darwin, was the first to point out that the innate response to tickling is squirming and straining to withdraw the tickled part. If a fly settles on the belly of a horse, it automatically makes the muscles around that spot contract—the equivalent of squirming in a tickled child. This is an instinctive reaction, meant to escape attacks on sensitive parts of the body like the soles of the feet, the armpits, belly and flank. The horse does not laugh when tickled; however the child laughs, but not always.

The interesting thing is if you try and tickle yourself in the same spot where you are 'oh-so-ticklish' when touched by another person, you will find that you don't feel ticklish at all! It obviously means that your reaction depends upon who tickles you! Therefore, both the body as well as mind play a part in the feeling of ticklishness.

A child will laugh only when he perceives tickling as a mock

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attack, that is, he knows that the person tickling is pretending to attack him without meaning any harm. For the same reason, people laugh only when tickled by others and not when they tickle themselves. Scientists carried out experiments at the Yale University in the USA, where they found out that the babies, less than one year old, laughed fifteen rimes more often when tickled by their mothers than by strangers. They mostly cried when tickled by strangers. This was because they understood that their mothers were playing with them for fun, but with strangers they were not sure.

Some scientists have suggested that tickling excites certain small, fine nerve endings just beneath the skin, especially on the palms and soles. The first and most obvious reaction to this is laughter. In addition the pulse quickens, the blood pressure rises, and the body becomes alert.

Try this out: sit in a group of people, all of whom you should not know. Close your eyes and ask any one of them to tickle you. See how you react!

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'Although we know,' the sphinx did say, 'How falls the night and what brings the day,

We still haven't found out the reasons why We sometimes laugh and sometimes cry.'

Laughter And Tears

What makes people laugh? You would be surprised but scientists are still trying to find out the answer. In fact, the best explanations that we have are still only theories, without any firm evidence.

Here is what we know about it. Laughter is an expression of many feelings and is found only among human beings. Psychologists continue to study two basic questions about laughter—what makes people laugh? And what is the purpose of laughter? They think that an odd or abnormal situation or things provoke laughter, and that laughter helps people to release their extra energy, get rid of tension, flush out their lungs, and make social contact.

What we do not know is why people laugh. Laughter is spontaneous act mostly, which involves the contraction of fifteen facial muscles and is accompanied by certain irrepressible noises. It is an activity that is not related to the struggle for survival,

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unlike breathing, eating, drinking and reproducing. What this means is that human beings will not die if they do not laugh. However, they will become very tense and depressed and may require a psychiatrist's help if they do not laugh for long periods. Although laughter is a unique reflex in that it has no apparent biological purpose, it does have great psychological value. It provides relief from tension.

If that is all we know about laughter, what about crying? What makes people shed tears? Certain glands in the eyes produce tears. Tears are essential to bathe the eye and they carry no germs, that is, they are sterile. Each human tear gland is in the upper and outer part of each eye and they produce tears continuously. It is surprising that even though the eye is warm, constantly exposed

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to air throughout the day, blinked over and open to evaporation, only half to two-third of a gram of tears is produced in a day Laughing, yawning, coughing, vomiting also induce tear production, in addition to bright light, wind, foreign bodies, infections, inflammation and, of course, emotional triggers. Onions give off a strong-smelling substance that irritates our eyes, and in order to protect ourselves from this irritation, we 'cry'. When the flow is greatly increased, as in crying, the tears flow over the eyelid onto the cheek. A 'good cry' will certainly produce in excess of half a gram of tears. All vertebrates produce tears, but no animal other than man has shown that it can weep in response to some form of sadness or shock.

Although crying and laughing are opposites in terms of the feelings that trigger them off, they involve many of the same brain circuits and muscles. We know this from the fact that there are patients who, having brain damage, lose control over laughing as well as crying.

So we, human beings, are special. We are the only creatures that laugh and cry. What does it matter that we do not yet kiio vV why?

KJ / \ KJ

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7 will show you some fun,' the sphinx smilingly said. And as I watched curiously from my bed,

I saw big, fat bubbles come bobbing in a spray, From a sudsy tub, they danced their way.

Of Soaps And Suds

Surely you have had fun with soap bubbles at some time or the other? If you have not, try and work up a good lather in a bucket full of soapy water, try and blow bubbles through a ring. You will see the most beautiful colours inside each bubble as it gently bobs along.

Why does soap form a lather with water? Why does not a mixture of, say, milk and water lather?

You probably know that if oil and water are present together, the oil will float on top of the water, and a thin oil-water boundary will be seen between the two layers. To understand detergent action, you will have to remember this simple fact.

First, let us understand what we mean by a soap or a detergent. Anv substance that enhances the cleansing action of water is called a soap or detergent. This is made up of a cleansing agent called a surfactant. A surfactant is a special t) pe of molecule which has

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a long tail and a short head. The head likes water and turns itself towards water while the long tail dislikes water and turns itself away from water. It is a special property of surfactant that it allows oil and water to become friends with each other. Thus, a bunch of such molecules in water will line themselves so that the water-hating tails point away from the water. These tails are fond of grease and oil, and it is here that the grease from the dirty clothes, that we wash, goes and collects itself. Thus a layer of oily dirt and soap floats on top of the water and soap mixture. This gets washed away when we rinse the dirty clothes.

Had there been no soap, the oily part of the dirt would not have left our clothes, as you know that oil and water do not mix. It is as if the surfactant shows its head to the water (which the water likes), and its tail to the oil (which the oil likes). Now the surfactant sits in the boundary between the oil and water, rather like a link between two enemies. The surfactant is also known as emulsifier.

Any substance, not necessarily only soap, that has the property of collecting at an oil-water boundary is called a surfactant or emulsifier. Soap or detergent is only one such example. Every surfactant will have some detergent action, to a greater or lesser extent. Foam is formed when the oil-water boundary is shaken hard by air, when excess soap present allows the air to enter into the soap-water mixture and form bubbles. This is why we need excess soap to form a lather, we cannot hope to get lather if we are stingy with the soap! The amount of foam formed has nothing to do with the cleaning power of the soap, as there are excellent detergents that cause little foam and there are poor detergents with high foaming power.

So do not get fooled by a sudsy soap! It may or may not be a good detergent.

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'You are old and wise,' I stopped to say, 'How is it that your hair turned grey?' 'Yours will, too,' my wise friend said,

'Our age is shown right from the head.'

Will My Hair Turn Grey?

As you know, hair is made up of dead cells. In fact, hair is nothing but dead skin. In the cells of the hair, however, there is a substance that is absent in skin, called keratin. It is this substance that makes hair hard and strong unlike our soft skin. Keratin is also found in fingernails, cat's claws, horse's hooves, the scales of crocodiles and the feathers of a bird such as the sparrow.

Each hair is rooted below the point where it joins the skin. It grows from a tiny pocket called a follicle, fed by tiny blood vessels that nourish the hair roots and make them grow.

The colour of a person's hair depends largely on a substance called melanin. This is the name of the pigment that is contained in hair cells at the time when they are formed in the root. Special cells called melanocytes make this pigment. All human

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beings have the same number of melanocytes, but the activity of these cells varies among individuals and races. Some races have more active melanocytes that make more melanin. This is the reason why people of different races have hair of different colours. (In the case of red hair there is an additional pigment present.)

It is the amount of this colouring in the cells that makes the hair dark or light. As people grow older, less and less melanin is contained in the newly-formed melanocytes. Owing to this, hair gradually turns grey or white.

It has been found by some scientists that shock can turn the hair of a person grey, though why this happens is still not clear. Some feel that shock or worry cause less pigment to be deposited in the hair, while others feel that air bubbles begin to appear in the hair after shock. The presence of air bubbles in place of pigment in the hair makes it look grey.

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We hardly spoke when there was a crash, As thunder broke, we made a hasty dash

To the nearest shed, and a grand hailstorm Started with a bang, on a day so warm.

Whence Comes This Hail?

Hailstones are messengers from the heavens above. If only they could speak, they would be able to bring us tales of the skies so far, above us! Actually they do speak, but in their own language, which we must try to learn. A hailstone's shape, colour and size are its way of telling us about its origin and the place it has come from.

Hail usually forms at a height of two to seven miles above the surface of the earth. So you see, these small pieces of ice have come from regions of atmosphere that you and I can only dream of! What is more, they need warm weather to form. The reason is that hot air rises up from the earth's surface, expands and cools rapidly during this expansion. It cools to very low temperatures and rises so fast that raindrops are carried along with it, up to the regions where the air gets very cold. There it meets with snow which is found at these temperatures on mountain tops and forms pellets of cloudy ice. It is interesting to note that rings of hard, clear ice are formed if freezing occurs slowly, and milky layers are formed if freezing occurs so quickly that bubbles do not have time to escape. So a hailstone has its story of creation hidden in its structure. A cloudy hailstone tells that it froze very rapidly, while a clear one tells of its slow formation. In fact, a cloudy stone has entrapped within it bubbles of air from up to seven miles above!

The largest stones are of grapefruit or softball size while the smallest are pea-size. For a hailstorm to occur, the weather must be warm and the region must be mountainous. The most favourable conditions occur in the USA, Russia and Argentina.

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The high mountainous region of Kenya also has a very high incidence of hailstorm.

Hailstones spend some time dancing within the cloud that formed them! Wind drafts carry the stones up and down within the cloud and in the process they form their layered structure. Finally, when they are too heavy to stay up above, they fall swiftly to the earth. Some fall at a speed close to 88 miles per hour, while many fall at 22 to 44 miles per hour.

A hailstone really comes down to us, dancing its way from the regions above! The next time you see a hailstorm, take a close look at a hailstone. You can understand its unspoken language if only you care to look.

'Come, sphinx, relax, for you must be In need of a refreshing cup of tea.'

I paused, as the sphinx laughed to say: 'Do you know why tea cheers up your day?'

Care For A Cup Of Tea?

Can you imagine life without tea? The drink that serves as a refresher for more than half the world. What is so special about it anyway? What gives tea its flavour? And why is it that some teas have a stronger flavour than the others? (When you are feeling tired and sleepy, a cup of tea works

wonders on your mood. It lifts your spirits and makes you feel more energetic. This is called a stimulating effect j /There are three main properties that tea possesses—its

refreshing (or stimulating) quality, its special flavour, smell (called aroma) and lastly, its colour and pungent taste. Scientists have found that the first quality is due to the presence of a compound called caffeine, the second due to an essential oil, and the last

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due to compounds called tannins. (In fact, tannins are responsible for the brown colour of barks of trees as well.) Tea tannins have a bitter taste.

The flavour of tea depends both upon the type of plant as well as the method used for processing it. Fermented or black tea is processed by allowing it to get exposure to oxygen, and this results in a beverage that is amber-coloured, and is without bitterness.

Another form of processing yields what is called semi-fermented or oolong tea, which is made by partial exposure to oxygen. The leaves are allowed to wilt partially in the natural way, either by spreading them on trays in the factory or in the

Rolling machine for processing tea

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A -

Tea leaves being treated in steam

sun. After this, the leaves are rolled and 'fired' at high temperatures. Such varieties of tea are often scented with flowers, like jasmine, to yield pleasant-smelling tea. I Green tea is a third variety of tea that has been processed by

first sterilizing (killing the germs) the leaves, in steam or over charcoal fire. Treated leaves are then rolled and fired. In India tea is generally made by this process^)

You can see that tea must necessarily taste different depending upon its origin and mode of processing. Tea-tasters have the interesting job of finding out the taste of different types of tea. They sip cups of tea made from various varieties and record the taste and flavour. In one study tea-tasters were given tea that had no aroma at all, and even though the compounds that were responsible for their taste were still intact, none of the tasters recorded any flavour for the tea! If the cup of tea that is served to you has no aroma, you might not be able to detect a taste! So you see how important it is to tempt the palate with a pleasant aroma before taking a sip!

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'When I drink a liquid all too quick, Why is it, sphinx, that I go hie?

And once I pause to stop my breath, Why do the hiccups meet their death?'

Hie, Hie, Hie!

There is pin-drop silence in the class. All the students are writing their mathematics test with full concentration. You are still chewing the last morsel of lunch quietly, since you had no time to eat during the break. All of a sudden, you find yourself going, Hie, Hie, Hie! As everyone turns to look at you, you turn pink with embarrassment and stop your breath for a few seconds. Lo and behold! When you take the next breath your hiccups have disappeared! Has this ever happened to you?

Hiccups are short sounds produced by the automatic movement of a muscle that lies at the base of the chest, the diaphragm. The diaphragm separates the chest cavity from the stomach cavity. This is a dome-shaped muscle that contracts and relaxes to draw air in and out of the lungs. Breathing in means

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that the diaphragm contracts and breathing out means it has to expand. Normally these movements of the muscle are gentle and take place in a quiet rhythm. However, if you eat something which either makes your stomach expand too fast or irritates the inner lining of your stomach's wall, this will make the diaphragm contract suddenly. This automatic muscular movement is called a spasm. Immediately you will take in a breath by yourself since the contraction of the diaphragm and breath intake are linked activities. But this breath will be cut off by the automatic closure of the little opening between your vocal chords. It is this opening (the epiglottis) which prevents food from getting into the air passages leading to the lungs. The movement of the vocal chords will produce a characteristic sound, Hie! Naturally since breath intake is what started it all, by stopping the breath for a few seconds, the whole process of hiccuping will come to an end.

Hiccups seldom last more than a few minutes. Rarely do they last several hours. People can stop hiccups by breathing deeply, drinking or holding their breath.

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Left, Left, Left-Right-Left!

And now, my child, I will speak to you Of left-handers, who with left hand do

All their work, and drink and eat, With their left hand they will even greet.'

Most people prefer to use their right hand for eating, writing, holding things and doing work. However, people differ considerably in the range of activities for which they prefer a given hand. They also differ in the skill of each hand for various types of activities.

Why do most people use mainly their right hand? Scientists do not agree on the origin of this preference. Some people believe that right or left-handedness is inherited, which means that children of left-handed people have a greater chance of being left-handed. Others feel that a child is trained to being right or left-handed and, there is no natural preference for an infant. Still others feel that there are forces within the mother's womb that make the foetus inside prefer to use its right hand.

It is possible that all three hypotheses are true. It has been found that left-handed parents more often have left-handed offspring than right-handed parents have. Even at birth, most babies tend to move one arm—usually the right—more than the

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other. When scientists tried to prevent the infants, in a study, from developing a preference for one hand, they were unsuccessful, the infants still ended up preferring the particular hand at the end of the study. It was also observed that most babies shift their preference in the first year at least once.

There is some evidence that human beings have it in their genes to be more prone to right-handedness. Photographs of the fingerprints of a foetus have been found to indicate the use of the right hand more than the left during the fourth and fifth months of the foetus's time in the mother's womb. The debate is still on among scientists on whether preference for using a particular hand is acquired and learnt behaviour, or is it instinctive.

The human brain has two big halves, the left and the right half. Each half has nerves that cross over the level of the neck and go to the opposite side of the body. Those who believe that the genes dictate the choice of a person in using a particular hand say that the left half of the brain (which sends messages to the right side of the body) is stronger in a right-handed person, while the right half of the brain (which sends orders to the left half of the body) is stronger in a left-handed person. There is, as yet, no firm evidence for this, it is still a theory that needs more proof to substantiate it.

By far, most children are right-handed but psychologists discourage parents from forcing those who are not to switch over from the use of left hand to the right. Although many children have been successfully trained to use and prefer the right hand for any activity with no harmful effects, it is generally agreed upon by scientists that children who are left-handed should be allowed to remain so.

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I now asked the sphinx of choppy seas, Of jumping waves that toss as they please:

'What happens to the life within? Do creatures live or just sink in?'

Life In The High Seas

Can you imagine how it must feel to be living in the sea? Always tossing and moving, living creatures within the ocean must be constantly on the move themselves. For them stillness must be a thing unknown. What happens to them when the ocean currents are very strong like during a storm? How are the fish and other creatures able to survive?

It is believed widely that at one time (more than 450 million years ago), life existed only in the seas and fresh waters. So it is

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not surprising that there are still many more living creatures in the sea than on the land. The ocean teems with over 200,000 species of living organisms. Most sea life occurs in shallow waters where light penetrates and allows photosynthesis to take place.

However, most of the ocean has very little life. There is abundant life only in certain regions and man has already set up fisheries in these regions. Current fluctuations occur in many parts of the world and this is probably why there are some good and some bad years of fishing.

Sea animals and plants adopt different techniques for survival in the choppy waters. Creatures that live in the deep ocean spend their entire lives moving through water. Only their swimming stops them from sinking into the dark depths. It is known that many species swim several hundred vertical feet each day in response to varying light conditions, while others prefer the more

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or less permanent twilight conditions of deep waters. Near the shore there are no dark depths, for the bottom is within the reach of sunlight. The floor near the shore is crowded with living things that 'sit' rather than swim.

There are certain sea anemones, which hide in cracks and crevices where the sun does not shine directly on them. So they do not dry up and can retain their moisture. Other species survive by ganging up in groups so that bits of shell and debris stick to their body mass and catch moisture. Such groups may be exposed to direct sun for hours but they can still survive. Still other animals in the sea wear hard protective shells which they close protectively during periods of exposure. There are 'splash zones' where relatively few animals dwell. Only snails and microscopic plants can be found there. The majority of marine organisms are adapted to living in saline waters withstanding extremes of temperature and mechanical shock. There are animals that handle shock by attaching themselves tightly to rocks in order to avoid being swept away. Seaweed has to be very tough as it is found only in shallow water where the waves beat to and fro. It is for this reason that there are fewer kinds of plants in the sea than on land as not many varieties can survive the tough seas.

Those animals that cannot change themselves do the next best thing, they move their houses! They go and live where the ocean fluctuates only between certain ranges of temperature, light, salinity and currents. Scientists call them biological indicators, since their very presence shows that the particular region has these characteristics. Deeper down the water is out of reach of the waves and is quiet. Here the bottom of the ocean is covered with animals that feed on the small organisms that drift down from the surface, some of them crawl around on their legs while others fix themselves to the bottom permanently

How clever you have to be to survive the ocean currents! Are you not lucky to be a creature that lives on the land?

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I now wanted to know the reason why When for some reason my skin turns dry,

Why it starts to itch and itch, What does dryness have to do with it?

Scratch, Scratch!

When the weather turns dry or cold, you surely must have experienced your skin turning dry too. If you live in a very cold part of the world, you may even find that it wrinkles up and itches so much that you feel like scratching it. Your feet, face and hands must be the most affected as the skin in these parts of the body gets maximum exposure.

Skin is the largest organ of the body and the only one exposed to the outer world. It plays a very important role. It keeps out foreign substances (like bacteria, sharp objects, and water), retains fluids, protects us from harmful raj s, cools us when hot and keeps heat in when cold. It makes an important vitamin (vitamin D), receives signal (or stimuli) from the environment and excretes water, salt and organic compounds.

Skin is only 0.4 to 3 millimetres deep. Have you heard the saying, 'beauty is skin-deep'? It means a person's beauty is only from the outside layer, as thin as the skin. For the skin to remain beautiful, it needs to be soft and smooth. The water present in

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the skin should not dry up when the weather is dry as that will make the skin look wrinkled and cracked. The fat produced by the skin is the best insulating material against moisture, as oil and water do not mix. So the water from the skin cannot evaporate when it is covered by a layer of fat. Owing to the fat layer, water does not wet the skin readily but runs off it, thus preventing a cold feeling due to evaporation. As a result of washing with soap, however, the fat layer is dissolved and any trace of it is removed when we dry ourselves with a towel. After washing, skin lacks oily layer and is much more sensitive to outside influences than before. During wet and cold seasons we cannot do without the protection of the fatty layer of the skin.

Skin is actually one of the busiest organs in our body. It manufactures billions of new cells daily and sheds billions of dead cells. The dead cells are found on uncared for skin and will come off with clean stocking or underwear as these are peeled off the body.

When the pain nerves in our skin are stimulated just a little, we do not feel pain but we feel itchy instead. Certain small fibres in the top portion of the skin are moved by a gentle stimulus, like insects or fabric, to produce a sensation that we call itching. Dry skin does not have any fat layer on it and dead cells are exposed. Itching is the body's signal, 'Remove dead cells! Apply a layer of fat!' Scientists still do not know why skin is the only organ in the whole body that can feel an itch.

'Sphinx, I have noticed one strange thing, ' I said, 'When my baby sister is sleeping,

She seems to smile and suddenly pout, Although she does not wake when I shout!'

Smiling Babies

Do you have a baby brother or sister? You may have spent some time near the crib, if you have one.

If you have seen a baby asleep in its crib, you may have noticed that it seems to smile and pout in its sleep. What makes a baby do that? When a baby smiles for the first time, parents feel a great sense of happiness, which more than makes up for their sleepless nights! Yet many child psychologists are of the opinion that a baby's earliest smiles do not necessarily mean what his or her parents imagine they mean!

It is believed that there are three kinds of smiling in infants. Reflexive smiling occurs in newborns, usually when they are asleep or nearly so. This is not a typical smile in that it lacks the crinkling around the eyes that usually marks a true smile, and is a fleeting response to no particular stimulus. What this means is that a newborn baby smiles in its sleep by itself and without any known cause. Although some scientists felt that the earliest smiles are linked to the gas that forms inside a baby's body after it feeds, present-day scientists do not agree with this.

Non-selective social smiling begins from two to eight weeks after birth. The smile is now a full-scale, crinkly-eyed one that comes -w"hen the baby is wide awake. At this point, the baby smiles without choosing what or whom to smile at. It will smile equally well at its parents and family as well as at strangers. The baby will smile even at a piece of cardboard with two dark circles suggesting eyes!

Finally, at the age of five or six months, babies reach the stage of selective smiling when most of their smiles are reserved

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for their familiar caretakers. Some psychologists feel that a baby's smiling is often not a social response like an adult's but an expression of the infant's delight in learning that his own behaviour can make something happen, for instance, he may smile when he discovers that every time he flings up his arms, someone gives him a playful poke in the ribs.

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' Why is it, sphinx, that the barks of trees Can't have just any colour they please,

Brown in colour, all look quite the same, But trees differ in flower, fruit and name?'

Barks In Uniform

Nature has used her paintbrush to splash colours over flowers, fruits, birds and animals, but she seems to have run out of ideas when it comes to barks of trees. All of them are brown, perhaps varying only in the particular shade.

Why is this so? Nature must surely be very wise with a purpose behind the creation of coloured petals in flowers. If flowers were not so attractive, bees and butterflies would not go to them so easily to suck their nectar and cause pollination. Without pollination, how would flowers reproduce? It is their beautiful appearance that draws these flighty messengers to flowers and ensures the survival of their species. Barks of trees, on the other hand, do not have any such function. Their role is to act as a firm support for the tree without any need to look attractive. What is important is their hardness, toughness, height and width, rather than their colour. So nature has concentrated on these aspects of the bark of a tree by making it a firm and solid support.

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Further, the main chemical compounds present in the bark of a tree, called tannins, are brown in colour. They lend the uniform colour to the tree's bark, the particular shade varying owing to different amount of tannin present in different trees. This is the reason why the barks of all trees are brown in colour.

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/ • • f /ave you ever wondered what makes you laugh when someone tickles you? Or why some people are left-handed and some right-handed? Or why do babies smile in sleep? Well, how about a sphinx to answer these and many more such queries as and when they occur to you? The book explores, with the sphinx, the scientific principles behind the day-to-day happenings. It is necessary to wonder why and to know the answers in some degree!