A CBT PUBLICATION

MARVEIS o f SCIENCE

Children's Book Trust, New Delhi

These chapters are largely a collection made from entries in the category Popular Science in the Competition for Writers of Children's Books organized by Children's Book Trust.

Illustrated by Nilabho Dhar Chowdhury EDITED BY GEETA MENON

Text typeset in 12/16 pt. Southern

© by CBT 1997

Reprinted 1999, 2002, 2004, 2006, 2008.

ISBN 81-7011-784-4 All rights reserved. No part of this book may be reproduced in whole or in part, or stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. 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@cbtnd.com Website: www.childrensbooktrust.com

CONTENTS

Earthquakes

Kalyani Chitrao

Volcanoes

T. Pakshirajan

Sound

R.K. Murthi

A Force Called Friction

Rupa Talukdar and Dr. Rina Dutta

The Law of Gravity

T. Pakshirajan

Rooting for Radar

Roopa Pai

Lever Power

R.K. Murthi

81

Autobiography of an Atom

Dr. K.V.K.K. Prasad

Louis Pasteur

Manimala Das

Laser

R.K. Murthi

Nano-Tech

Dilip M. Salwi

92

105

118

131

1 EARTHQUAKES

September 30, 1993. The

date is inscribed deep in our

memory. Indians, particularly

those from the grief-struck area

of Maharashtra, will never be

able to forget that terrible day.

It was at 2 a.m. when, all of a

sudden, without any warning,

the residents of Latur and

Osmanabad were shaken out of

their sleep. Within a few

seconds, nearly 28,000 of

them perished, thousands were

seriously injured, hundreds lost

their homes and personal

belongings and buildings were

destroyed.

What frightful power had

caused the damage? It was

neither flood nor hurricane. It

was not a bomb either. Latur

and Osmanabad were struck

by a violent earthquake that

measured 6.2 on the Richter

Scale. On this scale,

developed by the American

scientist, Charles Richter in

1935, a strength or magni-

tude of 2.0 or 3.0 indicates a

weak earthquake, while 6.2

means a strong one. The two

districts had obviously suffered

a strong earthquake.

The tremors of the earth-

quake were also felt as far as

Gujarat, Goa, Karnataka,

Andhra Pradesh, Kerala and

Pondicherry. The energy

released by the quake was very

high, equivalent to 10 atomic

5

On January 24, 1556, a major earthquake struck the province of Shensi in China killing over 800,000 persons. This ancient Chinese earthquake detector functioned on the principle that an earth tremor would open the dragons' jaws, so the balls dropped into the mouths of the toads below,

v

bombs of the kind dropped on

Nagasaki during the second

world war.

Beliefs

Hundreds of years ago,

people all over the world had

strange ideas about.earth-

quakes. Some believed that a

very large animal or god held

the earth in his possession and if

he moved, coughed or sneezed,

there was an earthquake.

In our ancient lore, for

example, the earth was a plat-

form that rested on the back of

eight big elephants. When one

of the elephants was tired, it

lowered and shook its head,

causing the ground to tremble.

In the Celebes Islands, in

Indonesia, people thought that

the earth was supported by a

giant pig. Earthquakes occurred

when the pig scratched itself

against a palm tree.

The ancient Greeks blamed

the giant man, Atlas who carried

the earth on his back—that the

earthquakes occurred when he

shrugged his shoulders.

However, as science advanced

and people gained more under-

standing of earthquakes, these

legends were replaced with new

theories.

6

The solid core is surrounded

by a layer of liquid core. Next

comes the lower mantle, which,

in fact, is the main bulk of the

earth between its core and its

surface. The mantle, in turn, is

surrounded by a fudge like layer,

the asthenosphere. The litho-

sphere which is about 30 kms.

thick and floats on the astheno-

sphere includes the crust, the

hard surface of the earth on

which we live.

The lithosphere can be

considered as a very thick shell

with several cracks. Each area

surrounded by crack lines forms

what is known as a plate.

Scientists have given names to

these plates. For example, a

large part of India lies on the

Indian plate. Much of the

United States is situated on the

North American plate. There

are many other plates such as

the South American plate, the

Pacific plate and so on: In fact,

these plates are not stationary;

they move in relation to each

other. The study of these plates

and their movements that cause

earthquakes is known as

platetectonics.

7

Today, the awful disaster of

Osmanabad and Latur, and, as a

matter of fact, earthquakes in

general, have a scientific

explanation. They could be best

understood if we begin by

studying the physical composi-

tion of the earth.

Earth's layers

If we were to slice the earth,

we would be able to see its

layers. At the very centre is the

core, about 2 ,500 kms. in

diameter. At a depth of about

2 ,900 kms. from the earth's

surface, the core is believed to

be made of molten iron,

possibly with a solid centre.

The island country of Japan is subject to intense crustal movements and violent earth-quakes and volcanic activity. Over 565,000 earthquakes were recorded in Matsushiro, Japan, between August 1965 and December 1966. On one particular day, 661 earthquake shocks were felt by people, and 7,000 were recorded by instruments.

Stress in the rocks owing to the pressure where plates move alongside each other resulting in a fault. A. Tension increases B. It is released in a sudden jerk. 1. Fault line 2. Pressure setting up stress in the rocks 3. Slip 4. Shock waves 5. Epicentre

Ocean plate

Under some oceans, plates

fall apart in areas often called

spreading zones. These zones

or gaps between plates are filled

with molten rock known as

magma, rising from deep within

the earth. When this magma

cools, new plate materials are

formed. As a result, plates

expand horizontally.

When the edge of a horizont-

ally expanding plate meets

another plate, something is

bound to happen.

As the plates meet at a place

called subduction zone, one

plate tries to move under the

other. This movement of plates

releases powerful forces within

the earth's surface. Some of

these forces caused by

subduction, are released in the

form of an earthquake. The

intensity of the earthquake

depends upon the amount of

force released during this inter-

plate activity.

On September 19, 1985, a

violent earthquake shook

Mexico. It was caused by sub-

duction. Here, a part of the

Pacific plate met the North

American plate. On that

particular day, very high

pressure was built up between

the plates and was released as

energy causing a terrible

earthquake.

8

Aftershocks

Apart from interplate activity,

it may be noted, some earth-

quakes are caused by the force

that builds up around a fault in

the earth's surface.

Faults could be described as

large cracks on the earth's

surface or as unstable regions

on the earth's crust lying bet-

ween two plates. They are

usually defined in terms of

geological time or, in other

words, the span of history,

dating back to almost four-and-

a-half billion years, as known

today.

Any fault where the move-

ment of plates has taken place

in recent geological time is

called an active fault. On the

other hand, a fault where there

has been no plate movement for

millions of years is known as an

inactive fault. The movement of

the earth's crust along an active

fault produces a large amount

of pressure in the lithosphere.

When this pressure is released,

there is an earthquake.

Most big earthquakes are

followed by aftershocks. They

may be nearly as strong as the

main earthquake or simply

minor tremors.

Aftershocks may occur owing

to several reasons and may last

for minutes, days or even weeks

after the earthquake. In many

cases the pressure caused by

the movement of the earth

along a fault is not completely

released at the time of the main

quake. As a result, the

increased pressure is released in

the form of an aftershock.

Causes

Volcanoes can also cause

earthquakes. A volcano is active

when a spot in the earth opens

up. Steam, hot gases and liquid

rocks are ejected violently. This

liquid rock is known as lava.

When still inside the ground,

the lava is called magma. In

case of a volcanic eruption, the

magma is emitted at high

pressure, shaking the surface of

the earth around it.

Can we cause earthquakes? It

is hard to believe but it is true.

This happens when water or

9

wastes are pumped into deep

wells. As a result, a lot of

pressure is built on and within

the rock layers at the bottom of

the wells. If it is very high, rocks

move suddenly. This movement

causes an earthquake.

For example, in 1962, Rocky

Mountain Arsenal of the US

army near Denver, Colorado,

decided to dispose of a large

amount of waste by digging a

hole into the earth. There had

been no earthquakes in the area

around the hole in 80 years.

However, one month after

pumping of waste into the

ground, this area was hit by an

earthquake. When the pumping

of waste had stopped by 1968,

no earthquake was recorded.

But during those few years, the

quiet arsenal area had more

than 1,000 earthquakes.

Earthquakes, whether caused

by man, by volcanoes or by high

pressure on ocean beds or

around the fault along the

surface of the earth, are not

always easy to detect. Some of

them are too small to be

located, others occur in thinly-

populated areas.

Seismograph

Seismology is the study of

earthquakes. By examining the

effects of an earthquake,

seismologists can learn more

about its causes. To detect

earthquakes they use a special

device called a seismograph.

A seismograph is made of a

hanging weight, a moving piece

of paper and a pen attached to

the weight. When the weight is

steady, the pen draws a straight

line on the paper. But when the

weight vibrates, the pen draws a

wavy line. Each segment of the

wavy line denotes a single vibra-

tion. Seismologists attach the

weight to a rod going deep into

the earth. In this way, they are

sure that only the earthquake

vibrations would make the

No earthquake has ever been recorded that has quite meas-ured 9 on the Richter Scale. However, the earthquake that destroyed San Francisco in 1906 measured 8.3 and the one that struck Anchorage, Alaska, in 1964 registered 8.5 on the Richter Scale.

10

Seismograph 1. Frame transmits earth's vibrat ions to wire 2. Wire 3. Heavy weight 4. Pen 5. Seismograph 6. Rotat ing paper drum 7. Frame 8. Base set into the ground 9. Horizontal earth movements

weight move. Seismographs

have helped scientists discover

that earthquakes generate three

types of waves, namely,

Primary waves, Secondary

waves and Surface waves.

In primary waves (also called

pressure waves), the particles of

matter travel back and forth in

the direction of the wave

motion, very much like a coiled

spring. Whereas, the particles

in secondary waves (also called

shear waves) oscillate at right

angles to the wave motion like a

vibrating spring.

Primary waves are the fastest

moving waves. They can be

heard as a low rumble. You can

imagine a primary wave as

squeezing and releasing the

earth as it travels through it and

a secondary wave as making the

earth move to one side and then

to the other.

The third kind of waves,

called surface waves, are waves

that move along the surface of

the earth. Surface waves are

created when primary waves

and secondary waves from the

earthquake reach the earth's

11

surface. They move slower than

primary waves and secondary

waves but they last longer and

are known to circle the earth

several times before departing.

There are two types of

surface waves—Love waves and

Rayleigh waves. The Love

waves, named after the British

scientist, A.E.H. Love, vibrate

horizontally. They can destroy

surface structures, shaking

buildings until they crack and

collapse.

The Rayleigh wave is named

after the British scientist, Lord

Rayleigh. These waves move in

elliptical orbits, in a rolling

motion, at a speed of 2.7 kms.

per sec., pushing the earth's

surface upwards. These waves

are not as dangerous as Love

waves because they mainly raise

the land. Rising and falling land

movements do not affect

buildings as much as land

movements that shake them

from side to side.

Since the primary waves

travel faster than the other

waves, they are the first to be

detected by a distant seismo-

graph; the secondary waves

come later. The farther a

seismograph is located from the

earthquake, the longer the time

between the arrival of the

primary waves and the arrival of

the secondary waves.

Seismologists measure the

time between the arrival of the

primary waves and the

secondary waves to find out the

force of the earthquake, the

focus or the place underground

from where the earthquake has

originated and the epicentre,

the place on the ground just

above the focus.

Monitoring

If detecting an earthquake is

not very easy, predicting it is

even harder. There is no reliable

way of finding out when exactly

an earthquake will occur.

However, scientists did think

of some methods of predicting

earthquakes. The most common

among them is the seismic gap

method. This method was pro-

posed in early 1970s by a

seismologist called Lynn Sykes.

The idea behind it was quite

12

4 O

Types of waves 1. Primary waves 2. Secondary waves 3. Surface waves 4. Wave direct ion 5. Compress ion 6. Expans ion 7. Love waves 8. Rayleigh waves

simple. As we already know,

high pressure builds up along

the fault that has not had an

earthquake for a long time.

Such an area is more likely to

have an earthquake than an

area which has had a recent

earthquake.

Special instruments such as

tiltmeters and magnetometers

are used to predict earth-

quakes. In a tiltmeter, two

water-filled chambers are

placed on the earth in an area

suspected of having earthquake

movements. Both the chambers

are connected with a tube. If the

earth rises or tilts beneath one

of the chambers, water runs out

through the tube and raises the

level of water in the other

chamber. A measuring scale

tells seismologists just how

much the ground has tilted.

Magnetometers are sensitive

devices that measure the dir-

ection of the earth's magnetic

field. Strain in rock can change

the field. Detection of this

change helps seismologists

understand that the pressure is

building up in the rock which

could cause an earthquake.

The focus of an earthquake is

under the earth. The distance

from the focus to the epicentre

is called focal depth. The

farther away a place is from the

epicentre the lesser the intensity

Earthquakes normally bring only destruction. But for the people of Santa Catering Desert, California, the massive earthquake that struck on February 9, 1956, was indeed a blessing in disguise. One of the cracks in the earth tapped an underground reservoir. When the earthquake struck, a well of fresh, sweet water spurted out of the ground!

13

Structure of an earthquake 1. Focus 2. Epicentre 3. Focal depth

of the earthquake there.

Seismologists have occasion-

ally been lucky—they have been

able to predict earthquakes and

save thousands of lives. For

example, in 1975, scientists in

China predicted an earthquake

in the town of Haicheng but two

hours before it struck. Millions

of people were evacuated and

the amount of destruction was

considerably reduced.

Protection

If, by predicting earthquakes,

we could save lives, what would

happen if we were actually able

to prevent them? We would not

only be able to save lives but

also prevent widespread

damage to property. But, is it

possible to prevent an earth-

quake? Many people believe

that earthquakes could be

prevented. One way of stopping

an earthquake is to grease the

faults where it takes place. This

may allow the plates to move

smoothly against each other

without building up the high

pressure levels that cause

earthquakes.

Another method involves

constructing earthquake control

wells. These are pits dug on the

earth's surface along a fault that

can be filled with water to make

the fault slippery. This would

lead to a mini-earthquake, too

small to cause any serious

damage but large enough to

help release some of the

pressure from the fault.

Earthquakes, as are known to

us, are natural events that have

taken place throughout the

earth's history. It is difficult to

prevent an earthquake, but as

our knowledge and under-

standing of the earth grows,

wise planning can reduce the

devastating effects of the

disaster. This can be done by

14

carefully monitoring the faults

along the earth's surface. It is

also important to construct

buildings that can withstand

earthquakes such as the

Empirial Hotel in Tokyo built by

an American architect, Frank

Lloyd Wright, which survived

the 1923 earthquake almost

undamaged.

On January 17, 1995, a

massive earthquake of the

intensity 7.2 struck Kobe and its

neighbouring areas in Japan. It

lasted for 20 seconds and

caused extensive damage and

many deaths. However, most of

the modern buildings, Kobe

Municipal Office Buildings for

one, withstood the quake.

There is also an increasing

need to educate people so that

they know what to do in case of

an emergency. When there is an

earthquake, it is advisable to

stay away from glass windows,

doors, almirahs and mirrors and

your effort should be to get

under a table or a sturdy cot to

avoid getting hurt by falling

objects. In an effort to get to

open space, you would rush

towards the doors or staircase

only to find them broken or

jammed. It is very essential that

all your electrical appliances

and cooking gas are turned off.

In Japan and California, for

example, earthquake drills are a

part of everyday life. Children

learn to keep a torch and sturdy

shoes by their beds, so that they

can get to safety if an earth-

quake strikes at night.

Ancient monuments along the coast of Japan carry the inscription, 'When you feel an earthquake, expect a tsunami', a piece of advice which tells of Japan's long history of tsunami disasters. Tsunami is a Japanese term accepted the world over. It is misleading to call them tidal waves. It is a wave that spreads from the centre of the disturbance, like the ripples from a pebble thrown into a pond. The energy stored in the tsunami is only about one hundredth of the total energy of an earthquake but it can equal the power of a 2.5 megaton nuclear weapon.

15

2 VOLCANOES

It was the early hours of

November 14, 1963!

We were close to a very

rare phenomenon happening.

The venue was the south-west

coast of Iceland near the

Vestmanneyjar islands. The

fishermen in the fishing-boat

'Iceliner II' were taken by

surprise. At a distance they saw

something unusual.

Suddenly ash and steam went

up to a height of more than

6,000 m.; lava poured out at

the rate of 5,00,000 tons an

hour and slowly a 'volcano'

rose up from the bottom of

the sea.

Three weeks thence a little

island was formed! It was about

3 sq. kms. wide and 152 m.

high. The island has been

named Surtsey in honour of the

Norse god of fire, and later

developed into a beautiful spot

noted for its flora and fauna,

with a well-equipped laboratory

for scientific study and research.

Sometimes islands born out

of volcanic eruptions amidst the

ocean are soon washed away.

In the immediate vicinity of

Surtsey another volcano

appeared in 1965, reaching a

height of 200 m., and was

given the name of Surtling. But

it was destroyed by marine

erosion.

Therefore, a volcano may

appear and disappear.

16

The island of Surtsey

Legends

What then is a volcano? How

does it act? Where can it be

found?

The term 'volcano' is a

derivation from the Latin word

'Vulcanis' or 'Volcanus'. Vulcan,

according to Roman mythology,

was the god of fire, originally

of volcanic fire, and patron of

metallurgical arts and crafts. He

was the son of Jupiter and

Juno, one of whom hurled him

from Heaven. As a result of the

fall he became lame. Later

legends say that Vulcan married

Venus, the goddess of love and

beauty, and this union added

grace and beauty to Vulcan's

craftwork.

Volcanoes are supposed to be

the chimneys of Vulcan's sub-

terranean smithies. Mount Etna

in Sicily is the most prominent

one. It was here that Vulcan

was supposed to have made

objects of art, arms and armour

for gods and heroes, and the

thunderbolt for Jupiter. Vulcano

is one of the Lipari Islands,

north of Sicily, and in the

classical times it was thought to

be the entrance to the nether-

world, the domain of Vulcan.

This is the mythological-back-

ground of volcanoes. Science

explains it differently.

Formation

• Millions and millions of years

ago, the sun was at the centre

Volcanalia, the fest ival of Vulcan, was celebrated by the Romans on August 23 each year with special rites to avert destructive fire.

17

of a huge cloud of gas and dust

which was whirling about in

space. At one stage, millions of

years ago, a big chunk of that

hot, gaseous cloud flew off.

With the passage of time this

big mass gradually cooled down

and finally took the shape of

our earth. This is one of the

many theories about the origin

of the planet.

Today the earth has suffi-

ciently cooled down and looks

like a ball of solid rock. The

surface, called crust, is thick

and continents are formed over

it. The surface temperature is

merely 60° C but 48 kms.

below, it is 1,200° C. At the

core or centre of the earth,

6,400 kms. below, the

temperature is 5,500° C, at

which temperature even rocks

would melt. Scientists believe

that at the core there is a huge

ball of molten iron 6,500 kms.

in diameter.

Thus, our earth, though

having cooled down on the

surface to permit life to

originate, is still too hot deep

inside. It is always shivering,

causing earthquakes every two

or three minutes somewhere in

the world.

When temperature rises, the

molten rock material, called

magma, at the centre expands

and, mixed with steam and gas,

forces its way out of the

interior to hit the surface of the

earth. When the water in a

kettle reaches boiling point, the

steam throws off the lid with

force and escapes. In the same

way the magma escapes with

enormous force through the

cracks or fissures on the hard

crust of the earth. This is an

eruption.

When the magma reaches the

surface, owing to the drop in

pressure and physical and

chemical changes it becomes

lava and flows over. It cools

into rocks. When eruptions are

repeated, layer after layer is

built up and, in course of time,

a cone-shaped mountain of rock

stands in that place. This is a

volcano with a crater or

depression or opening at the

top through which the lava is

forced out in an eruption. Some-

times the materials may flow

widely over the country rock.

18

Some volcanoes may sleep

for a while and suddenly wake

up to renewed eruptive activity.

These are the dormant ones.

Extinct volcanoes are those

that have long ceased to erupt

and cooled down. These may

be found in areas with no sign

of any volcanic activity at

present.

The earth has about 850

active volcanoes of which 80

are submarine. The number of

dormant and extinct ones will

be many thousands.

According to one estimate,

about two-thirds of world's

active volcanoes occur along

the coasts of the Pacific Ocean,

the graphically named 'Pacific

Ring of Fire', which covers the

island arcs of eastern Pacific

Ocean and along principal

mountain belts in the western

parts of North and South

America. Of the recorded

2,500 eruptions, two volcanoes

appeared in and around the

Pacific Ocean where there are

not less than 336 volcanoes.

The notable ones are mounts

like Lassen, Baker, Rainier,

Crater Lake, Hood and Shasta.

19

Distribution

From the above we see that

volcanoes are not found every-

where but only along those

spots on the earth's crust which

are too weak to resist the

pressure of lava from the

interior. These weak spots may

be on land or under the sea.

Volcanoes are classified into

active, dormant and extinct

ones. One which is definitely

known to have periodically

erupted in historical times, with

gases, lava, ashes and other

fragmentary materials flowing

out through the vents, is an

active one.

When Mount Vesuvius fell quiet 28 hours after its eruption in 79 A.D., the entire city of Pompeii was wiped out. However, in destroying it, the volcano pre-served it for all time. Many of the 20,000 inhabitants were killed and their remains can be seen in whichever position they died, trapped by the hot ash and pumice. This city was unearthed by an archaeologist, Giuseppe Fiorelli, in 1767.

Active volcano 1. Ash and gas cloud 2. Crater 3. Vent 4. Laccolith 5. Sill 6. Dyke 7. Magma chamber 8. Hot molten lava 9. Cone 10. Lava flow 11. Rock strata

South Alaska, the Alaskan

peninsula and the Aleutian

Islands form one of the world's

most volcanically active areas

where a chain of 80 active

volcanoes stretching nearly

3,200 kms. in length is found.

In South America most of the

highest peaks are volcanoes.

The Japanese Islands, Kuril

Islands, Philippines and the line

running through Indonesia

towards New Zealand are prone

to volcanic activity. In Japan,

the snow-clad Mount Fujiyama

is the most famous, rising to

3,776 m. within 24 kms. of

the sea. To the Japanese, it is

the most sacred mountain and

symbol of their art and culture.

Hawaii, Tonga and Samoa

are volcanic cones rising from

the ocean floor. In East Africa,

there are volcanoes like

Kilimanjaro (6,440 m.) and

Mount Kenya (5,198 m.)

20

Volcanic activity is widespread

in Iceland. Several Atlantic

islands too have volcanoes. The

West Indian arcs have indication

of past volcanicity and a few

active ones.

Seamounts, also called

'guyots', are among the best

known submarine volcanic

structures. Sometimes they rise

to within 800 m. of the surface

and form isolated islands. There

are about 10,000 seamounts in

the Pacific.

An island

Very rarely new volcanoes

may appear as did the island of

Surtsey mentioned in the begin-

ning. During the emergence of

Surtsey, two more little islands

started coming up only to

disappear in a few days. At

times, to beat the turbulent

waves as it were, the volcano

comes up with quick repetitive

eruptions and establishes its

ascendency by forming a

A. Extinct volcano B. Lava plugs 1. Crater lake 2. Plug 3. Eroded volcanic plug

permanent island. The island of

Anak Krakatoa in Sundra Straits

between Java and Sumatra, and

the island of Falcon in the

Tonga group originated in this

way. (In 1883 most of the

main island of Krakatoa dis-

appeared in a big explosion.)

Just like the fishermen of

Iceland, the people of Mexico

had the rare fortune of

witnessing an amazing phenom-

enon in February 1943. In

front of their eyes a volcano

rose up from the bosom of the

earth in the middle of a corn-

field. Within a year it formed

into a cone 325 m. high. It

was named Paricutin. The

steam and lava that issued from

it took a heavy toll of two

cities. Nine years later it

abruptly fell silent.

Only one man survived the volcanic eruption of Mount Pelee in St. Pierre in 1902. He was a prisoner who was in jail awaiting trial for murder. His prison cell was so far under-ground that the ashes and gases did not reach him. He was rescued four days after the eruption.

.

Eruptions

Eruptions differ according to

the pressure inside the volcano,

the amount of gas in the

magma, and the nature of the

lava, which may be runny or

viscous. Two major forms of

volcanic eruptions are noted by

volcanists. In the central erupt-

ive form, the eruption takes

place from a single vent or a

group of closely related vents.

When lava wells up along a line

of weakness or fissure in the

earth's crust, the lava is emitted

from the whole length

simultaneously or at intervals

along the fissure. This is linear

eruption and it can cause

gigantic lava floods over large

areas.

Such eruptions emit a variety

of materials. Usually, the most

important product of an

eruption is lava, the magma

which reaches the surface. The

form of a volcanic cone largely

depends upon the nature of this

lava. If the lava contains much

silica with a high melting point,

it solidifies quickly and does not

flow very far. This kind of lava

22

material may solidify in the vent

and cause recurrent explosive

eruptions. Silica lava builds

high, steep-sided cones. On the

other hand, lava that is relati-

vely poor in silica, rich in iron

and magnesium minerals, is

called basaltin lava. With lower

melting point, such lava flows

for a considerable distance,

before becoming solid.

The solidification of lava may

take different forms like the 'aa'

(pronounced as 'ah-ah'), the

'pahoehoe', and the 'pillow'

types, all of which are

Hawaiian names.

The 'aa' type solidifies into

irregular block-like masses.

Solidified lava having a

wrinkled, rope or cord-like

surface is called the 'pahoehoe'

type. If the lava solidifies like a

pile of pillows, probably under-

water, it is known as the

'pillow' type lava. Some pillow

lava in the Canadian Shield

volcanoes is the oldest known

dating 2,800 million years. In

the Hawaiian eruptions, lava

flows from the vent and piles

up in low shield-like volcanoes.

Icelandic eruptions are quiet.

The magma contains very little

gas and explosions do not take

place but runny lava pours from

the cracks in the ground. In

Strombolian eruptions gas in

the magma shoots ash in the

air during explosion. Vulcanian

types contain more viscous

magma and the gas in it

periodically explodes bits of

hardened crust into the air.

Vesuvian eruptions are even

more explosive and huge clouds

of ash rise from the vent. Such

eruptions are often accompan-

ied by torrential rains and, as a

consequence, the fine dust

material flows down the slopes

as a stream of mud which

causes enormous havoc. In

Pelean eruptions (named after

Mount Pelee in West Indies) hot

gas and bits of magma erupt.

Plinean eruptions named after

the Roman writer, Pliny who

recorded the eruption of

Vesuvius in 79 a.d., are most

explosive. There are no lava

flows. Instead the gas-filled

magma is shattered into ash

which rises several kilometres

into the air.

In 1915, Mount Lassen in

23

Types of eruptions 1. Icelandic 2. Hawaiian 3. Strombolian 4. Vulcanian 5. Vesuvian 6. Pelean 7. Plinean

North California poured out

gases along with glowing lava

fragments devastating a wide

forest area. It is referred to as

"The Great Hot Blast".

In some cases eruptions are

accompanied by a series of

explosions and solid materials

7 ar if -awife-:; ""*"""" Iif**'*''**'***̂ ^

such as pieces of country rock,

fragments of solidified lava,

finer materials like pumice,

cinders, dust and ash (generally

known as, 'tephra') are ejected.

The 3,700 metre-high volcano

Irazu in Costa Rica slept for a

long time and suddenly woke

24

up in March 1963, to pour out

dry acid dust, ruining nearly

650 sq. kms. of area.

Another strange phenomenon

is that small amounts of liquid

magma thrown out into the air

may solidify before hitting the

ground in the form of globular

masses. They are known as

'volcanic bombs'.

According to experts in volca-

nology, most of the volcanoes

are in the nature of issuing

warnings before erupting. These

may be in the form of mild

local earthquakes, intermittent

explosions or emission of

smoke from the mountain.

Many a time the authorities,

heeding these warnings,

evacuated the population of the

cities close to the volcanoes.

Types

Volcanoes are of many types.

In an 'explosion vent', a small

hole is blown through the rock

and it is later surrounded by a

low crater of rock fragments.

Such formations are seen in

Iceland, and in the middle

25

Volcanology is a very complex study. For an adventurous volcanologist it could even involve actually climbing to the very top of an active volcano. Even if the volcano is not actually erupting, the ground may be so hot that it could burn the shoes of the scientists and the gases may prove suffocat ing. Workers have actually looked through open craters into the bubbling, burning lava below.

Rhine Highlands.

In some places fragments of

solid material accumulate

around a vent to form a cone.

Such formation is called 'cinder

cone volcano'. Many such cones

are found in western USA.

Iceland has nearly ninety such

volcanoes rising to an average

height of 36-46 m. Monte

Nuova is an ash-cone lying west

of Naples. Its peculiarity is that

it came up in a single eruption

and rose up to a height of

more than 137 m. in just three

days. Paricutin, mentioned

earlier, is also a good example

of this type. Near Flagstaff, in

Arizona, lies a symmetrical

cinder cone 300 m. high; the

cinders at its top are tinted

pink and so the volcano is

nicknamed Sunset Crater. There

are a few volcanoes made

purely of ash like the Volcano

de Fuego in Guatemala.

In the case of some vol-

canoes, there may not be any

violent explosion or ejection of

fragments of solid material.

Instead, the lava flows smoothly

from the vent and builds a

volcanic form. Such a one is

called a 'lava or plug dome

volcano'. If the lava is viscous

(thick and sticky), it produces a

steep dome. Mount Lassen in

Northern California is an

example; it is 5,000 years old.

Basaltin lava can flow for

long distances and the vol-

canoes formed of it are called

shield volcanoes. The great

volcanoes of Hawaii islands are

of this nature. Such a volcano

has a broad crater (caldera)

often covered with thin layers

of solidified lava. The lava may

erupt through the crater or

through cracks in the sides. The

caldera contains a composite

pit. Other pits form in cracks

on the shield of the volcano.

Hawaii is a group of 20-odd

islands of which eight are large.

The Hawaiian islands are the

tops of great volcanoes. The

island of Hawaii, with an area

of 10,400 sq. kms. is the

biggest. In fact, it is twice as

large as all the other islands

put together and is known as

'The Big Island'. It is the result

of five volcanic eruptions over-

lapping one another.

According to Hawaiian

legends, the goddess of

volcano, Pele, made these

islands rise from the bottom of

the Pacific Ocean and every

now and then she comes to the

islands' craters to kindle her

fires into eruption.

Mauna Loa, with a broad,

shallow crater that is 16 kms.

in circumference, is yet active

and erupts every few years. Its

summit is 4,175 m. above sea-

level. On its flank, there is

another cone named Kilauea

that is 1,219 m. high. Muana

Kea, the loftiest volcano in

Hawaii, is an extinct one, half

immersed under the water and

half above sea-level.

The most common and

26

Principal types of volcanoes A. Plug dome B. Cinder cone C. Shield D. Composite

typical volcano is the composite

cone. It is also known as

Strato-Volcano. This kind is the

creation of numerous eruptions

spread over a long period of

time. Most of the world's

highest volcanoes fall under this

category. In this there will be a

major cone with many

secondary cones on its slopes

as Etna in Sicily has. When

Etna erupted in 1971, lava

flowed out through several vents

on its flanks.

Some volcanoes have many

major cones and are termed

27

'multiple volcanoes'. Ruapehu

and Tongariro in New Zealand

are of this nature. Stromboli in

the Lipari Islands has had

frequent gentle eruptions, at

intervals of an hour. The glow

of its hot lava on the clouds of

smoke above the crater earned

it the name of "the Lighthouse

of the Mediterranean".

Many volcanoes, after a long

period of silent slumber, may

come up with vengeance as did

the Vesuvius. The last large

eruption of Vesuvius was in

March 1944. Such sudden out-

bursts may blow off the summit

cone leaving behind a shallow

cavity called a 'basal wreck' or

caldera. Crater Lake in Oregon,

U.S.A., is one such caldera.

Aso in Japan is the largest.

A variety of minor volcanic

forms associated with volcanoes

nearing extinction deserve

mention here. One of them

called a 'solfatara' refers to a

volcano emitting sulphurous gas;

a 'fumarole', on the other

hand, emits steam and other

gases; and a vent emitting

carbon dioxide is given the

name of 'mofette'.

Aftermath

During the formative years of

the earth, every part of it was

prone to volcanic eruptions. In

historical times (ever since

history was recorded), the

volcanicity was restricted to

particular areas, and now, large

parts of our world are free

from the eye of the god of fire.

Volcanoes bring large-scale

death and destruction to the

cities close to them. The hot

lava with a temperature of about

1,600° C easily burns out large

areas. The ash, steam and gases

can play havoc on human lives.

History has many such

instances, a few of which like

Mount Vesuvius have been

mentioned earlier. In 1783, the

ashes ejected by Laki in Iceland

caused famines and epidemics

claiming 10,000 lives. Similarly,

thousands of people were

sacrificed at the altars of

volcanoes like Unzen-dake in

Japan, Tambora in Indonesia,

Krakatoa in Malaysian islands,

Kelud in Java and one of the

world's largest active volcanoes,

Kilauea in Hawaiian islands.

28

Volcanic region 1. Crater 2. Cone 3. Pipe 4. Dyke 5. Sill 6. Hot spring 7. Fumaroles 8. Laccolith 9. Geyser 10. Fissure flow

Volcanoes are useful too.

They can create natural lakes.

A lava flow may block the

outlet of a valley and form a

lake basin. More, the craters of

extinct volcanoes can serve as

nature's big bowls of water like

the Crater Lake, in Oregon.

Coral polyps are tiny marine

animals. Strangely enough, their

skeleton grows outside their

bodies to protect and support

the body of these animals.

When the polyp dies, the

skeleton left behind makes the

coral. Billions of these skeletons

form into coral reefs and

islands. Charles Darwin, the

famous naturalist, studied deeply

about coral reefs and came to a

conclusion. An undersea

volcano rises above the water

and in the shallow waters

around the island, corals begin

to build up a reef. If the

volcano happens to sink com-

pletely, the wide area of coral

reef remains with a lagoon in

the centre.

In some areas of past or

present volcanic activity,

thermal springs are found from

29

which hot water containing

mineral substances flows out

continuously. In Iceland, there

are thousands of such hot

springs which are used for

central heating and supplying

swimming pools with water.

The hot water ejected with

much force is, in some cases,

accompanied by steam and an

intermittent paroxysmal

fountain. This is called a

'geyser'. Such geysers are also

found in Iceland, Yellowstone

National Park in U.S.A. and

the North Island of New

Zealand. These hot springs are

useful as laundries and baths for

treatment of physical ailments.

For many years the steam of

fumaroles has been used for

heating schools and public

buildings in Japan and Iceland.

Boric acid can be produced

from such natural steam.

A kind of cement, known as

hydraulic cement, made by

mixing volcanic ash with lime,

was used by Romans in the

second century.

Man has learnt to live with

volcanoes around him because

it is the same benevolent

Mother Nature who made the

world look wonderful with

colourful flowers, green plants,

cool rivers, blue seas and

majestic mountains, who also

created the volcanoes probably

as temples for the god of fire!

3 SOUND

We are living in a world of

sounds. There is an infinite

variety of sounds.

Some sounds are pleasing, like

the purr of a cat, the hum of a

bee or the notes of a koel, while

some are frightening, like the

roar of a lion, the growl of a

panther or the burst of an

explosive.

Some notes are loud; some

are low-pitched; some are shrill

while some are squeaky.

What is it?

Sound, in essence, is vibration.

If you happen to stand near a

field of paddy, the stalks appear

to be swinging and dancing in

the wind. The air carries the

vibrations of the stalks. You can

even give tunes of your favourite

song to this sound.

R.L. Stevenson, who was

once travelling by a train, taught

the train to sing a song he loved.

In the clatter of the wheels,

Stevenson could hear the song.

What Stevenson did with the

train, you can do with the notes

you hear near a field.

We can produce sounds, if we

can create vibrations. Reach for

a branch of a neem tree. Pull it

down. Then let it go. The branch

swings up and down cutting

through the air. The air vibrates,

we hear a 'swish'. This swish

31

becomes lower in tone. Finally it

dies when the branch stops

swinging.

There are many objects which

vibrate and give us sounds.

Pick up a thin sheet of paper.

Hold it against your lips. Blow

out air. The paper vibrates. We

hear rustling sounds. We notice

that the paper flutters. It moves.

These movements produce the

vibrations and the sounds.

Tie a long string to a peg and

stretch it taut. Tie the other end

to another peg. Then, tug at the

string. It vibrates as it moves

back and forth. The vibrations

reduce in range, slowly. Finally,

the string ceases to vibrate. It

does not produce any sound.

We notice that the sound is

louder when the string vibrates

more. The sound becomes softer

when the vibrations become less

intense.

It is this principle which is

used in many musical instru-

ments. In the veena, the metal

strings are plucked by fingers.

The violinist makes the strings

vibrate with the help of the bow

and his fingers. A guitarist

presses the strings with one hand

and plucks them with the other.

Pressing the strings changes the

notes by making the vibrating

parts shorter or longer.

The mridangam, the tabla,

the drum are called percussion

instruments. They are cylinders

or bowls with one or both ends

closed by a stretched 'skin'. Calf-

skin is generally used. The

vibrations or sounds made by the

drum depends on the size of the

skin, and how taut the skin is.

Vibration

Insects, animals, birds know

how to produce sounds. The

cricket is an insect that hides in

nooks and corners in the kitchen

during the day. At night, once

the lights are off, it comes out. It

produces grating notes.

One of the fore-wings of the

cricket has a vein on the under-

side. This vein looks like a

toothed file. The edge of the

other wing has a ridge. This acts

as a scraper. When the wing with

the scraper (the ridge) rubs

against the other wing (which

has grooves or teeth), occur the

vibrations. These vibrations

produce the grating sound.

Often, the insect finds its mate

by showing its skill in producing

such notes.

We can produce a similar

sound. Pick up a comb which

has teeth close to each other.

Run the comb along the edge of

a table or desk. The teeth vibrate

making a sound resembling the

cricket's.

The grasshopper makes a

comparable sound, with a

slightly different technique. It

rubs its hind legs against the

wings. This causes vibrations

which result in sounds.

Birds have a vocal organ called

syrinx. It is made of a bony

band. The band is attached to a

membrane. The membrane is

fully stretched. It is attached to

muscles. The bird forces air

through the lungs. The air rushes

out, playing on the membrane. It

vibrates according to the

pressure of the wind. These

vibrations become the notes of

the bird. Each bird produces a

different note. These depend on

the nature of the membrane and

33

The stethoscopes doctors use have two tubes that allow them to use both ears to listen to sounds inside the body. The sounds they hear tell them whether the patient being examined is well or not.

its capacity to vibrate.

Musical instruments like the

flute, the nadaswaram and the

shehnai use the principle of

vibration. The flautist, for

example, blows into one of the

holes drilled in the flute. The air

rushes in. There are holes

through which the air can

escape. But the flautist closes

some of the holes, opens others,

making the air seek different

routes of escape producing

varied notes. As the air rushes

out, it vibrates.

Animals produce sounds by

forcing air through the voice box.

Human voice

Animals produce limited

sounds. Man alone is capable of

making wide-ranging sounds. He

can talk, shout, scream, cry, sing

or whisper.

How does man produce

sounds? What provides such

range to the human voice?

Listen to the Aeolian harp, for

an answer. This is a stringed

musical instrument, played by

the wind. The Aeolian harp gets

34

its name from Aeolus, god of

winds. It consists of a sound box

which is about three feet long

but only five inches broad and

three inches deep. The strings of

varying thickness are tuned in

unison.

The Aeolian harp is usually

placed by the open window or

hung out of the door to catch

the wind. The air blows over the

strings and they vibrate making

musical notes.

There is an organ in our body

called Adam's apple. You can

feel it, as you run your fingers

from the chin downwards. It is in

the middle of the neck. It is a

bone-like structure, rather firm.

Put your finger on the Adam's

apple. Now make soft notes.

Turn out louder notes. You will

find the Adam's apple vibrating,

differently, according to the

sounds you produce. The

Adam's apple vibrates as air

rushes over it.

Vocal cords in your throat vibrate and make sounds as the air from the lungs is pushed over them. The mouth and lips form these sounds into words.

Medium

But how does sound reach us?

It does not travel in vacuum. It

needs a medium to travel.

The earth is always in motion.

It goes round its axis, once every

24 hours. It also goes round the

sun. It takes 3 6 5 ^ days for each

trip. Yet, we do not hear the

slightest sound of the earth's

movement. The air and the

atmosphere move with the

earth. There is thus no medium

to take the sound around.

When there is a medium, the

vibrations spread, very much like

eddies in a pool.

Vibrations move through many

mediums. Generally, it is the air

around which is the medium.

These vibrations move in all dir-

ections. If we are in their path,

they reach our ears.

The human ear consists of

three parts. They are the outer

ear, the middle ear and the inner

ear. The vibrations are collected

by the outer ear, called the

auricle. They pass through a

canal which widens towards the

middle ear or the ear-drum. It is

shaped very much like a loud-

speaker. The ear-drum vibrates,

lets the vibrations play on two

bones, called the tympanic

bones. Then they swing along

the fluid in the inner ear. The

inner ear is like the shell of a

snail. It is called the cochlea.

The vibrations make waves in

the fluid. They pluck the organ

of corti, a miniature harp like

organ with about 20,000

strings. Each string is short,

hardly a few hundredths of an

inch in length. Each string

responds to a defined note. This

note is its pitch. The pitch is

decided by the number of

vibrations per second. The brain

gets each sound distinctly. The

brain gathers the sounds which

35

1. Nose 2. Mouth 3. Larynx 4. Windpipe 5. Lungs 6. Tongue 7. Vocal cords

1. Middle ear 2. Ossicles 3. Inner ear 4. Hearing nerve 5. Cochlea 6. Membrane 7. Ear-drum 8. Ear canal 9. Auricle 10. Outer ear

come in successively, hears and

understands the sounds.

Air is not the only medium

through which sound moves.

Pick up two empty tins.

Remove their lids. Drill a hole at

the bottom of each of the tins.

Insert a string, of about 10 m.

through the holes. Fix it at the

bottom of the insides of the tins.

Ask a friend to hold one of the

tins. Move away with the second

tin till the string becomes taut.

Now speak into the tin while

your friend holds the mouth of

the tin to his ear. He hears what

you say. Now it is his turn to

reply. You listen by holding the

tin to your ear.

The vibrations, in this case,

have been carried from the base

of the tin by the string. It is the

medium.

We have seen that vibrations

need a medium to travel. It could

be air or string or a block of

wood or a piece of metal or even

water.

Sound travels better through

liquids and solids than gases.

Light travels faster than the

sound. On rainy days, when

there is thunder and lightning,

Sound moves through the air at 1,158 kmph whereas light moves at 299,000 km. per sec.!

36

we see the lightning first much

before the thunder.

Pollution

The pitch or frequency of a

sound refers to the rate of

vibrations per second. The

intensity or loudness is measured

in decibels. A decibel is one-

tenth of a bel and a bel 'is a unit

used in comparison of power

levels in electrical communication

or intensities of sound'. The

level of tolerance of a human

ear is 90 decibels. At 130

decibels, the sound hurts the

ears. That is why we plug our

ears when a jet aircraft takes off,

for it produces notes of about

150 decibels. People who live

close to airports suffer various

degrees of deafness, over a

period of time.

A wag defined noise thus:

'Noise is wrong sound, in the

wrong place, at the wrong time.

The world has become far too

noisy now. Those who live in

cities are specially exposed to

noise continuously. Noise causes

headache, nervous damage and

depression.

There are many sources of

noise pollution. There was a

time when people used to

commute on foot as there were

few vehicles. Now, most people

have their own conveyance.

Noise pollution is caused by

the constant honking of horns;

also, when people do not turn

off their engines when they wait

at traffic crossings.

The loudspeaker which is

played at the time of marriages,

festivals or during elections is yet

another source of noise pollution

in India.

In factories, old machines

produce very loud sounds, much

above the tolerable limit of 70

to 90 decibels. Sooner or later,

the workers in such factories are

bound to acquire one or the

other disease.

Thanks to the efforts of the

environmentalists and various

voluntary organizations the world

over, people have become aware

of the need to control noise.

How do we fight noise

pollution?

The noise caused by traffic can

be brought down by improved

silencers for automobiles. The

sounding of the horn in front of

hospitals, nursing homes and

schools is prohibited.

As far as the use of the loud-

speakers at a function is

concerned, it should be used

only for the people attending the

function and not turned towards

the neighbourhood.

To control the noise pollution

in factories, machines should be

regularly oiled. Soft padding can

be given to those parts of the

machine which move backward

and forward or up and down

many times.

Paul Leug, a German scientist,

came up with a machine in

1933. He showed that noise,

which moves in waves, has its

crests—the highest points—and

troughs—the lowest points. Leug

used this knowledge to produce

silence.

Take any noise. Identify its

crests and troughs. Then produce

another noise from the opposite

direction which has a

corresponding pattern of crests

and troughs. Make them bump

into each other, so that the

crests of one hits the troughs of

the other. The two noises now

cancel each other. The result is

silence.

However, the patent which

Leug developed was crude. The

device did not have much scope

for application. It only showed

the way to control noise

pollution.

Now, computers and micro-

electronics have joined hands.

They are providing new and

better equipment to control

38

noise pollution. The basic

principle remains the same.

Every irritating noise can be

killed by a corresponding noise.

All that is needed is a control on

how the two waves meet. If the

crests of one always run into the

troughs of the other, both noises

die out. Silence prevails.

Varied effects

Sound waves are very power-

ful. When there is thunder,

windowpanes rattle. The sound

waves released by thunder have

enough force. Anything that is

loose or not firmly held in place

quivers with the sound.

Sound waves can be very

destructive, too. Much of the

damage which a bomb causes

comes from sound waves. In a

bomb explosion, the TNT

(trinitrotoluene) charge affects

those objects or living things

which get the direct hit. The

sound waves released by the

explosion run wild. At times,

they destroy vehicles; factory

sheds and even buildings collapse

when they are hit by powerful

sound waves.

Is sound all evil then?

Certainly not.

What is music but sound. Yet,

is not music something that gives

us much delight? We swing to

the music which has lilt and

melody. We dance to the rhythm

and beat in the music.

In 1985, Larry Dossey of

Dallas Diagnostic Association,

said, "Music is medicine." He

used music to cure his patients of

headaches, stress and strain.

Music has a soothing effect on

human nerves.

The power of sound waves is

used to cure stones in the

kidney. Till recently, surgery was

the only method. Now, doctors

use the lithotripter which emits

powerful sound waves. These

waves are directed towards the

stones which break into bits. The

broken bits of the stone are

flushed out of the system.

Sound waves are also used to

In an avalanche, a mass of snow suddenly slides down a mountain. A loud sound can cause an avalanche. The sound waves disturb the snow and start it moving.

39

clear blocked arteries. Doctors

use sonography (use of ultra-

sound waves) in pregnant women

to check the development and

growth of the foetus.

When Prince Ulysses was

seriously injured and writhing in

agony, one of his men knew the

power of music. He asked all his

colleagues to stand in a circle

around Ulysses. Then he began

to sing. The others joined in.

The music was soothing. As it

filled the air, Ulysses relaxed.

Music helped Ulysses recover

faster.

There are many other areas

where sound helps.

Professor Stuart Campbell of

the Cancer Research Campaign,

at King's College Hospital,

London, used ultrasound, in

1983, to detect cancer of the

uterus.

He knew sounds do not go

through obstacles. Like light,

which comes back from a

reflective surface, sound bounces

back when it hits an obstacle.

Professor Stuart sent waves

directed towards the womb.

They came back. By studying the

angle and mode of their return,

Professor Stuart learnt a lot

about the state of the womb. He

could find out if the volume of

the womb had increased. These

held hints of a possible tumour

or cancer.

Echoes

Returning sounds are called

echoes. An echo is the reflection

and repetition of a sound from a

wall or inside an enclosed space.

You get to hear this effect when

you are in the valley of a hill.

Bats have poor eyesights. Yet

they can fly because they are

good at understanding echoes.

We often call someone who

bumps into obstacles as being

'blind as a bat'. But the bat does

not bump into trees or rocks or

other obstacles.

The bat, when it flies, lets out

high-pitched sounds. The notes

vibrate about 30,000 to 70,000

times per second. We cannot

hear these notes. These vibra-

tions spread out in all directions.

Some of them run into obstacles.

Then they bounce back. The bat

judges the echoes. It knows

40

where the obstacles are located.

It adjusts its flight path

accordingly.

Echoes are exploited to map

the bottom of the sea. A ship

sails out into the sea. It sends out

sound waves. These waves move

through the water. They hit the

sea bed. Then they come back as

echoes to the ship. The time

taken by the sound waves for the

two-way journey is recorded.

We know the speed at which

sound travels through water. It is

about 19,000 kmph. So, it is

possible to calculate the depth of

the sea at a given point.

Successive readings give the

relief of the sea's bed. This

technique is called echo-sounding

or sonar, that is, sound naviga-

tion and ranging.

Sound helps us in many ways.

There are machines which emit

sounds. These sounds are not

41

audible to us, human beings. Yet

they are received by some

animals. We can hear sound that

ranges from 20 to 20,000

vibrations per second. Any sound

caused by higher range of vibra-

tion, called supersonic sound, is

not audible to us. Cats, guinea-

pigs and rats can hear sounds up

to 30,000 vibrations per second.

When a machine creates sounds

of higher notes, the sound

becomes intolerable for some

pests. They run away from the

zone where the high-pitched

sounds prevail. There are pitches

which the mosquito cannot

stand. Sound is used, thus, to

keep pests away.

In 1992, two instruments were

fixed at the entrance to the

Taj Mahal. These let out sound

waves called ultrasound, much

Most blind people find their way through the busy streets with the help of echoes as well as direct sounds. Blind people of-ten become keenly sensitive to sounds. They can 'see' objects by the echoes that bounce off them, much as bats and por-poises do.

Man has learned to use echolocation mechanically too. Sonar systems, which give off very low sounds, are used chiefly underwater. They lo-cate icebergs, schools of fish, shipwrecks, and submarines.

V J

above the tolerance limits of the

human ear. It kept away the bees

that stung the tourists.

Doppler effect

In 1984, in Canada, such high

frequency sounds were used to

herd the caribou (North

American reindeer). These

animals migrate, every year,

near Hudson Bay. In 1984,

some of the rivers which lay on

the migration route were in

flood. About ten thousand

caribou drowned.

Eskimos are dependent on

caribou for meat. They make

clothes from their pelts. They

also make spoons, utensils and

weapons from its bones.

Eskimos decided to scare the

caribou by sounding high notes.

They flew over the area. Every

time they sighted a herd of

caribou, they sounded blaring

horns. The sound scared the

caribou. They turned back. They

did not head towards the rivers

in flood.

One wonders whether the

caribou felt the Doppler effect.

In 1846, Christian Doppler, an

Austrian physicist, discovered a

peculiar property of sound. The

whistle of a railway engine,

when the engine moves towards

42

you, is very shrill. Yet, when it

moves away from you, it sounds

much less sharp. Doppler found

that the sound waves from the

source that approaches us get

closer together as they reach us.

These waves arrive at shorter

intervals. So they turn shrill.

When the source of sound

recedes, the sound waves get

spread out. They come to us at

longer intervals. The sound then

loses intensity. You must have

noticed it.

Man has been exploiting sound

intelligently for several centuries.

The Golconda Fort near

Hyderabad is a good example.

The fort was very cleverly built so

that the ruler got to know about a

visitor even before he entered the

gate. The moment a visitor

opened his mouth even to whisper,

it was heard on top. This was

indeed a security precaution

made by the architect.

We have today mastered the

technique of recording sounds

on discs, tape-recorders and film

tracks. A world minus sound is

as unimaginable as it would be

uninteresting. Thank God for

sound!

Doppler effect

Do you think the seas are silent? No, they are not. The sea animals let out different types of sounds. The most intelligent among them is the dolphin. It uses 30 different sounds to communicate. It can hear sounds up to a distance of 24 kms. when it is under water.

4 A FORCE CALLED FRICTION

The peal of laughter at the

sight of a man who has slipped

and fallen is a common enough

happening on the roadside.

When such a mishap happens

to oneself, the humorous side

is replaced by a sense of sharp

pain. Why the pain? It is a

result of slipping on a rough

surface. How do we feel when

slipping down the smooth,

polished surface of slides in

school playgrounds and parks?

It is real fun! Supposing a

venturesome youngster tries to

climb up the slip, instead of

sliding down it? At every step

he will feel himself being pulled

down. In fact, he may not be

successful in reaching the other

end, unless, of course, he

wears highly rough-soled shoes!

You may start really wonder-

ing—what is all this about

slipping, rough surfaces and

smooth surfaces? The answer

lies in a very basic physical

property termed friction.

Physical aspect

Friction is a sort of force, or,

to be more specific, a hinder-

ing or retarding force. It comes

into play when an object moves

on the surface of another

object. The extent of this force

dictates whether an event will

be full of fun or tinged with

pain. Just try to imagine the

44

feeling of elation of a skier

traversing the slopes of

Kashmir or Switzerland! But

how does it feel to slip on a

banana peel? You may end up

with a fractured bone!

Apart from these incidents, a

look at your surroundings will

reveal the importance of friction

in everyday life. What is the

main principle behind grinding

grains in a chakki (mill)? The

answer is friction.

The friction comes into play

when somebody cleans soot-

stained or burnt utensils, when

you dump your clothes in the

washing machine; when you

write in your notebook, or even

when you run to catch your

school bus.

It is worth pondering that the

pre-historic man discovered fire

as a result of friction.

Inertia

Before going a little deeper

into the subject of friction, we

must try to understand another

important physical concept—

inertia. This concept was first

introduced by the British

scientist, Isaac Newton (1642-

1727). His Laws of Motion

deal primarily with two states

or conditions of a body—a

state of rest and a state of

motion. Inertia is a property

which is directly linked with

these two states of a body.

Inertia of rest is easy to

envision. If you keep a pencil

or a paperweight on your desk,

will it start to move on its own?

No, not unless you disturb it in

any way. To be precise, the

general tendency of a body at

rest is to continue to be at rest.

find a still smoother surface,

for example, a large sheet of

glass, the ball would cover a

still larger distance. If we

extend our imagination to a

resistance-free surface, an

object set in motion would tend

to go on forever, unless a

resistance is offered. In fact,

this is an elaborate way of

stating Newton's First Law of

Motion. It should be stressed in

this context that a resistance-

free surface is only a figment

of our imagination. In reality,

even the smoothest of surfaces

would reveal tiny cracks and

crevices when brought under a

microscope. In other words, all

surfaces, whether natural or

synthetic, offer some friction.

Most machines are designed

keeping friction in mind. This

is because friction steals energy

and turns into other forms of

Sir Isaac Newton

This concept may be

extended to a body in motion,

although it is a bit more

difficult to understand. Suppose

you roll a ball on the rough

surface of your playground. Do

the same thing in your school-

hall, which has a smoother

surface. You will see that the

ball rolls over a larger distance

in the latter case. If you could

Isaac Newton's three Laws of Motion are: 1. A body continues in a state of rest or uniform motion in a straight line unless acted upon by an external impressed force. 2. The rate of change of momentum is proportional to the impressed force and takes place in the direction of the force. 3. Action and reaction are equal and opposite. These laws were first stated by Newton in his Principia.

46

energy. However, it is virtually

impossible to get rid of it.

Even so for the sake of fun,

let us deviate from reality and

try to imagine what a friction-

free world would be like.

Suppose you are going to

school in your car or school

bus. Owing to inertia of

motion the tyres of your car

or bus would go on rolling.

You would eventually arrive at

your school-gate, but how do

you stop? Some sort of

resistance is necessary for

stopping! You would see your

school-gates being left behind!

In fact, once you are out of

the house, you may not be

able to come back! Just

imagine the uncontrollable

chaos that would result!

Contrarily, if this resistive

force were to reach infinite

proportions, then every object

in this universe would become

static. We would not be able

to move anything, even

ourselves! The writing of this

chapter would no longer be

possible. The concept of

smoothness would vanish from

the face of this earth, and its

place would be taken by

extreme roughness. Both the

above extreme situations are

undesirable.

Action, reaction

By now we are able to realize

that friction and sliding or

rolling are two faces of the

same phenomenon. Friction is

operative when the surface

offers resistance to motion.

When such resistance is

lowered, either by changing the

nature of the surface or by

external pressure, slide takes

over. To elaborate on this point,

suppose you place a wooden or

metallic box on a table. Owing

to inertia of rest the box will

not move on its own. Actually,

47

To play any game the muscles in your body provide the force that is needed to run, leap and jump. Short-putters need to be very strong as the shot is a heavy metal ball with a lot of inertia. It takes a big push to make it move away and fly through the air.

it is subjected to two forces

which balance each other. One

of the forces is its own weight,

acting downwards and the

other is the upward reaction of

the table. What do we mean by

the term upward reaction or

more precisely, reaction?

Newton discovered that for

every force there is an equal

and opposite force.

Have you seen anybody leap

ashore from a boat? As he

jumps forward, the boat is seen

to move backwards. At the very

moment of jumping, the man

applies a force on the boat.

This is called action. The boat,

in turn, provides an equal and

opposite force. It is this

reaction of the boat that

actually helps the man's for-

ward movement. The statement

of the third law is—to every

action there is an equal and

opposite reaction. What would

have happened if this were not

true? There would be no such

thing as balance or stability! If

the very ground we are

standing on does not oppose

our weight, we would sink into

the earth. In fact, our very

existence would be threatened!

Newton went a fairly long way

in unravelling certain secrets of

nature.

Varied

Now that we have under-

stood what reaction is, we can

say that the box on the table is

in a stable condition, scientific-

ally termed as equilibrium. If

you touch the box lightly with

your finger, it will not move.

But since a slight force has

been applied, an opposing

force, according to the third

law, would come into play. As

you go on increasing the force,

the opposing frictional force

would also increase. Since the

box is still in a static condition,

this frictional force is called

static friction. After a certain

limit, the pressure of your

finger will be able to overcome

the force of static friction and

the box will slide over the table.

When the box starts moving,

or sliding, the force opposing

its motion is called sliding

friction. By a similar argument,

if it was a cylindrical object

instead of a box, then rolling

friction would come into play.

It is important to note that the

condition when the box is just

about to slide on the table is

called limiting condition and the

magnitude of the frictional

force at that point is called

limiting friction. If you had

placed the same box on a large

slab of ice, you would have

49

required a lesser amount of

pressure to move it. In other

words, the magnitude of

friction depends upon the

nature of surface in contact. It

does not depend on the area

of contact. For example, you

would require the same amount

of force if the box had been

placed flat on the table or on

its side. Again, if you had

placed a heavier box on the

table, you would find that a

greater force would be neces-

sary to move it. For a given

surface, friction is also affected

by the weight of the body.

Slide

We have discussed (so far)

the concept of sliding friction

disturbing the equilibrium of the

box through pushing. Suppose

the box is placed on a wooden

platform and one end of the

latter is gradually raised from

the ground. Initially, the force

of static friction will prevent

the body from sliding down-

wards. When the platform is

sufficiently inclined, the box will

start sliding down under its

own weight. No external force

is necessary. You will notice

that the inclined plane makes

an angle with the ground. At a

certain angle, the box will not

actually slide, but will be just

on the point of sliding. This is

called the angle of repose.

If you have a look around

yourself, you will realize how

important inclined planes are.

Have you seen a motor-bike

being hauled across the steps

at the entrance to any building?

Usually, a wooden platform is

laid across the steps. Or heavy

objects like gas cylinders or

petrol containers being loaded

or unloaded from trucks? Here

also, inclined planes are used

and the objects are rolled up or

down them. These surfaces

serve as a means to reduce

friction and thereby ensure

lesser expenditure of energy.

Apart from such serious

applications, what do you think

of the slides in your park or

school playground? Do they not

serve as excellent examples of

inclined planes?

It has been explained that

50

friction is basically a hindering

force. From another point of

view, it can be looked upon as

an attractive force because it

resists breaking of contact with

the surface. Unless such

contact is broken, sliding can-

not occur. Thus sliding is a

repulsive force. If such attract-

ive forces are large, work or

motion would become

increasingly difficult and sur-

faces in contact would generate

excess heat.

Observe carefully a lane and

the nearest main road after a

drizzle. You will see that the

main road dries up faster.

Why? Because the frictional

heat generated by the tyres of

vehicles is enough to evaporate

the water. Another example is

based on the fact that all

metals expand when heated.

A gap or discontinuity left in

railway lines at regular intervals

allows the tracks to expand

when heated up. Otherwise,

the lines would expand and

become distorted. You can

expect the result—fatal

accidents!

In some cases, friction, along

with heat, may generate light.

Have you noticed sparks

generated by speeding trucks

on highways? Or when the

blacksmith sharpens your knife

or scissors against a revolving

wheel?

We have had a fairly detailed

discussion on friction along

51

with its advantages and dis-

advantages. Have you looked

for applications of friction in

nature? You will notice that

nature maintains a midway

between the two extremes—

friction and slide—so that there

is a perfect harmony in your

surroundings. Have you not

wondered at the similarity in

the shape of a bird soaring

high up in the sky, or a fish

gliding through water? Their

bodies have been shaped in a

way different from land

animals—in order to minimize

friction offered by air and water!

Vortex

The concept of friction is a

bit different with air and water

as they are both flowing

objects. In such cases, we talk

of internal friction or friction

between adjacent layers. If you

stir up your tea or coffee with

a spoon, you will see a sort of

miniature whirlpool. After some

time, the movement ceases.

This is due to friction between

adjacent layers of your tea or

coffee. When the friction

between them is minimal, the

flow is said to be streamlined

and the layers slide smoothly

over one another. When a solid

object (say, spherical or

cylindrical in shape, or having

many edges) is encountered,

the smooth flow is disrupted

and the layers tend to clash

against one another, forming

what is called a vortex.

Have you seen concentric

circles being formed when you

throw a stone in water? These

are called vortices. When such

vortices are formed, the flow is

called turbulent and such a flow

offers substantial resistance to

any object travelling through it.

As far as living things were

concerned, this meant that a

substantial amount of energy

had to be expended if they

were to overcome the resist-

ance offered by air and water.

Nature came out with an

excellent solution to the

problem.

Fishes and birds are endowed

with shapes evolved differently

from others. They are provided

with pointed frontal parts

gradually flattening out and

extending symmetrically out-

wards. Such a shape is called a

streamlined shape. This enables

an object to move through

without disturbing the flow.

Now have a careful look at

the fishes in an aquarium.

Their perfectly designed shape

is fascinating. However fast

they swim, you will not notice

any vortex formation in the

water. Have a closer look at

their mouths. They are pointed

but flatten out at the gills with-

out creating edges. You will

find a similarity with tips of

iron nails. They are made that

way to minimize the resistance

offered by surfaces into which

they are hammered (like walls

and wooden boards).

Nature's solution was also

adopted by marine and aero-

nautical engineers in designing

aeroplanes, rockets, submarines,

steamers and so on. As a result

of reduced friction, lesser

energy is required to drive the

engines, thus leading to lesser

fuel consumption.

53

Apart from these, we can

think of many other applica-

tions. Go for a stroll around

your nearest swimming pool.

Look closely at the specific

posture of a swimmer before

diving into water. You must

also be familiar with the

positioning of an athlete before

he starts running. These are

necessary so that entering

water or sprinting are done

with least resistance.

You are likely to have

realized that friction, combined

with slide, is an absolute

necessity for equilibrium. It is

also a way to explain certain

realities through simple physical

concepts.

5 THE LAW OF GRAVITY

The apple falls from the

tree. The flowers and leaves of

plants drop to the ground.

Anything we throw up comes

down. Why? Why do all objects

fall down? Why do they not go

up and stay where they are?

Is it not a miracle? Who

performs it?

Early studies

The great Italian astronomer,

Galileo Galilei, was the first to

study falling objects or bodies.

Born on February 15, 1564,

in the city of Pisa where the

world famous Leaning Tower

stands, Galileo first experimented

with different weights in his

laboratory to see how they fell

down.

Later, he is said to have

dropped simultaneously two iron

balls of different weights from

the Leaning Tower of Pisa to

prove some basic principles.

All objects tend to fall down.

If there is no air resistance, the

falling objects, irrespective of

their weights, hit the ground at

the same time. The speed of

the fall of bodies depends not

on their weights but on the

distance they cover during the

fall. A freely falling body has an

acceleration of 10 m. per sec.

55

But a body passing through air

does not gain speed at this rate.

A universal law

Galileo's experiment was only

to investigate how the bodies

fell to the ground. But it was

Isaac Newton, the renowned

British scientist, who found out

why the objects fell downward

instead of going upward (See

Newton's Laws of Motion in

Chapter 4, page 46). Newton

discovered the miracle per-

former. It was none else but

the immense power of

attraction of our Mother Earth

which pulls all unsupported

bodies towards her. This force

is known as gravitation or

gravity. It was one of the

greatest discoveries of man, for

it helped scientists to under-

stand many of nature's riddles.

Newton revealed the eternal

truth to the world. He formu-

lated his Law of Universal

Gravitation. According to this,

the force of gravity exists on

and in all objects, from the

tiniest grains of sand to objects

of huge proportions. Every

object in this world is endowed

with this power to attract

another. This power operates

according to the mass (amount

of matter) of the bodies and

the distance between them.

The bigger the objects, the

greater the force that pulls

them together. The farther

apart they are, the weaker the

force. The basic idea of

Newton's law can be explained

in another way. If the mass of

attracting bodies is doubled the

gravitational attraction becomes

doubled; on the contrary, if the

distance between them is

doubled, the force will be

reduced to one-fourth.

Gravity is imperceptible but it

can pass through any solid

matter. It only attracts and

never repels. That is to say,

56

For his achievements a measure of force has been named after Isaac Newton. A Newton is the amount of force needed for one second to give an object weighing one kilo-gram a velocity of one metre per second.

Without the force of gravity, everything on the earth—people, ships, houses, everything— would be flung out into space.

the power always draws a thing

to it and never pushes an

object away.

How strong is earth's

gravity? Why is it so abund-

ant? In what ways does it act?

Before we try to answer these

questions we should know some

basic facts about our earth.

Earth's pull

In ancient times, people

believed that our earth was flat

The force of gravity, working opposite to the earth's turning motion, holds us on the earth's surface.

and stood still at one place; the

sun and the moon circled round

it everyday and the stars

shining like diamonds were all

fixed to the canopy of the

heavens. Aryabhata, born in

476 A.D., was the first to

deduce that the earth is round

and that it rotates on its own

axis, creating day and night.

Solar and lunar eclipses

occurred because of the shadows

57

cast by the earth and the

moon. Nicholas Copernicus

(1473-1543), who was both a

Catholic priest and passionate

astronomer removed all illusions

and opened the eyes of the

people.

According to the Copernican

theory, the sun is at the centre

of a system called the solar

system and earth and other

planets revolve round the sun.

(Sole, the name of the Roman

sun-god, is the official name of

sun. Planet means wanderer;

the planets are all wandering in

a vast emptiness.)

We know that our earth is

neither flat nor still. It is

spherical and has two kinds of

perpetual motions. One, it

spins once in 24 hours (one

day for us) on its axis or

imaginary axis; two, it revolves

round the sun, once in a year.

Fortuntely, we do not feel

either of these motions. One of

the reasons is the play of the

gravitational force by which our

earth holds tightly the whole

creation to its surface and

carries us with it in its axial

rotation and journeys around

the sun like a mother walking

with her child on her hip.

How can earth have so much

force of attraction? The strength

of gravity varies with the mass

of the body. Scientists have

managed to calculate the

approximate weight of our

planet as 6,600 trillion tons.

Naturally, it can exert enorm-

ous gravitational pull, much

beyond our imagination, to

hold the entire world

population, crores of other

living beings and inanimate

objects to its surface.

A wizard!

Normally you can see the

magician who performs

amusing tricks. But gravity is a

wizard who is not visible. Yet

he performs many an incred-

ible miracles. He is a magician

par excellence. Let us see

some of his miracle.

Two-third of the earth's

surface is covered by vast

oceans. We are occupying only

the remaining one-third of the

land. In spite of earth's

58

constant rotation at a tremend-

ous speed, the ocean waters do

not flow over. No object on its

surface flies off. We do not roll

out of our globe. Gravity can

hold everything on the earth

down, including all the waters

in the seas and oceans.

The tides in the ocean are

caused by the interplay of the

gravitational forces of the

earth, the sun and the moon.

Like the earth, the sun and the

moon have gravitational

attraction and they constantly

pull the earth and draw the

ocean waters towards them.

Thus the sea rises and falls

twice a day causing high (spring)

tides and low (neap) tides.

The gravitational force works

in mysterious ways and benefits

us in myriad forms. We are

surrounded on all sides by a

vast ocean of air formed in

many layers which we call

atmosphere. This air too, like

any other matter, has its

weight. If all the air could be

collected, compressed and

weighed, it would equal

5,171 billion tons approximately.

Our earth contains more mass

and easily holds the atmo-

sphere in its grip. This

atmospheric covering serves as

a great armour provided by

nature for us against the

onslaught of some unsolicited

celestial bodies like meteors

(nearly 200 million of which

are estimated to enter our

atmosphere daily) and harmful

radiations from above. We are

accustomed to carrying the

weight of the atmosphere for

millions of years and so we do

not feel it at all.

Rain drops are brought down

to us by gravity and water is

the elixir of life. This indicates

that the gravitational force is

not confined to land alone but

extends up to some height

above the planet.

You may be surprised to

learn that the weight of our

body, our height and even our

59

The Moon has less mass than the Earth, so its gravity is much weaker. Astronauts weigh a sixth of their normal weight when they are on the Moon although their mass does not change.

Tide Earth Moon

Earth

Tide

Moon

Gravitational pull causes tides A. When the sun, the moon and the earth are in one line, spring tides occur. B. When the sun and the moon are at right angles to the earth, neap tides occur.

life span are greatly influenced

by the earth's gravity. Besides,

our spinal column, hands, feet

and all our limbs are tuned to

the play of this invisible power.

Thus for ages man has been

acclimatized to gravitational pull

and atmospheric pressure.

It is true that gravitational

force pervades all over the earth

but it acts strongly on the

seashore and grows weaker on

hilltops. Earth's gravity extends

only up to a certain limit beyond

which you will be completely

weightless and start floating.

Do you think that only our

earth and all the objects on it

have this miraculous power?

The sun, the moon, the stars

and all the planets have their

individual gravitational power

depending on their size and

mass which helps them to act

as they do.

The earth's path runs around

the sun. The sun's immense

gravity is always pulling at the

earth. But the earth does not

crash into the sun. That is

because the earth is moving

very fast; it has a lot of

centrifugal force.

Therefore the earth stays in

the same orbit as it goes

around the sun.

60

A

Sun

Space

Far above our earth, and

around it lies an endless

expanse of emptiness called,

'space'. You cannot conceive

how far and wide it extends. It

is all a 'void' and 'black' every-

where. It is neither cold nor

hot there. The outer space, as

we have known so far, has no

air or water. It is filled with

billions and billions of stars of

various sizes and colours,

clouds of dust and gas and

numerous other celestial

objects. All of them with the

encircling space make the

magnificent formation known as

the universe or cosmos. Every

particle in this cosmic system

has been endowed with the

power of attraction and has

been moving about in space for

countless years. That is why

Newton's discovery is referred

to as the Law of Universal

Gravitation.

Galaxies

A huge gaseous cloud

studded with millions of stars is

The sun holds the earth in its orbit

a galaxy. There are millions of

such galaxies in the universe.

In one galaxy lies our sun,

giving us abundantly the most

essential light and warmth. The

sun is after all a star, an

average-size star, among the

millions of stars in our galaxy.

Our sun is at the centre of a

big family of bodies going

round it at varied distances in

different periods of time.

Among them, nine are major

Centrifugal force

Gravitational force

61

planets, namely, Mercury,

Venus, Earth, Mars, Jupiter,

Saturn, Uranus, Neptune and

Pluto in the increasing order of

distance from the mighty ruler.

Except the first two, all other

primary planets are found to

have secondary planets

revolving round them. They are

called satellites. There are also

numerous planetoids or

asteroids, meteors, comets and

other planetary bodies circling

them. The planets have been

spinning on their axes and

simultaneously travelling round

the sun from their birth

millennia ago, in elliptical paths

called orbits. The entire forma-

tion, known in astronomy as

solar system, is only a frac-

tional part of our giant galaxy.

The most surprising fact is

that the sun keeps all the

countless members of its family

as 'life-captives' by its sheer

gravitational strength. The sun

has almost 99 per cent of the

mass of the entire solar system,

and is balanced on its own

gravity. The solar mass is

equivalent to 350,000 times

that of the earth. The sun is so

huge that thirteen lakh earths

can be conveniently packed

inside it. Nature has endowed

the sun with a gravitational

force 28 times that of our

planet. So it is no wonder that

the long hands of solar gravity

can envelop the entire system.

Mercury, the nearest at

58 million kms. and Pluto, the

farthest at 5,900 million kms.

are in the iron grip of the sun.

None of the planets can ever

escape or falter from their

orbits.

In proximity, the sun is our

nearest star at a distance of

150 million kms. So, the earth

which has the potentiality to

hold the entire mankind in its

grip is itself subservient to a

superior power. Newton studied

the planetary motions and

estabished that the entire solar

system is governed by the law

of gravitation.

More planets

In addition, Newton's law

helped the discovery of two

new planets. Ancient people

62

knew only six of the nine

planets and believed that there

existed no planet beyond

Saturn. In 1781, William

Herschel discovered the

seventh, a giant planet, named

afterwards as Uranus. Later,

when scientists noticed some

deviations in the orbit of this

new planet, they suspected that

another planet in the near

vicinity was exercising its

gravitational force on Uranus

and causing the perturbations.

The search for the unseen

planet was on and after a big

hunt, Johann Galle and

The solar system

63

The word 'galaxy' comes from the Greek for milk, 'gala'. Ancient Greeks believed the Milky Way was formed from milk spilled from the breast of the goddess Hera while she fed Heracles (Hercules).

Heinrich d'Arrest of Berlin

Observatory discovered the

eighth solar captive in 1846. It

was christened Neptune in

honour of the Roman sea-god.

The discovery of the ninth and

the present outermost planet,

Pluto in 1930 by Clyde

Tombaugh at Lowell

Observatory, in Flagstaff,

Arizona, was another great

triumph of Newton's theory.

One more example can be

cited to stress the importance

of the law of gravitation.

Regarding the origin of the

solar system, scientists have

offered various theories.

According to one hypothesis, in

the remote past, the sun was

at the centre of a cloud of gas

and dust (nebula). A star much

bigger than the sun came that

way and pulled on the sun with

extraordinary force. As a result

fragments of the sun were

blown off to whirl round in

space and, as time went on,

these gradually took the shape

of the planetary bodies.

Probably the whole solar

system owes its formation to

this universal law.

Johannes Kepler, another

forerunner of Newton, had

offered his laws relating to the

planetary motion in the solar

system. He observed that the

planets move faster when they

come closer to the sun, known

as perihelion, and slower, as

they go farther away, called

aphelion. For instance, our

earth runs at a speed of

30.2 kms. per sec. at perihelion

and slows down to 29.2 kms.

per sec. at aphelion. Similarly,

planets having orbits nearer to

the sun move faster than the

ones positioned farther away.

The speed of Mercury is at the

rate of 47.9 kms. per sec.

whereas Pluto runs at the rate

of 4.6 kms. per sec. In all

these cases, it goes without

saying that the miracle per-

former is the law of gravitation.

Jupiter, the super-giant

among the planets, has a

diameter of 1,42,880 kms. and

it is so voluminous that it is

equal to 1,300 earths. Since it

is composed predominantly of

gases like hydrogen and helium,

Jupiter has a mass only 318

times that of the earth's. Yet

Jupiter's gravitational force is

two and a half times greater

than the earth's. So we will not

be able to stand erect on

Jupiter as our weight would

increase by two and a half

times. Because of this

extraordinary muscle power,

Jupiter has pulled a few comets

out of their regular orbits.

In July 1994, a great cosmic

event took place. A comet,

named after its discoverers,

Shoemaker-Levy-9, was earlier

broken into 21 pieces by

Jupiter's gravitational influence

and since then it looked like a

long pearl necklace. This

64

Earth is the most highly coloured object in the solar system. From space it appears as a blue and white planet because of the oceans and the white of the clouds.

comet, being pulled still nearer,

collided with the planet in

July 1994 and all its pieces

went on bombarding Jupiter for

nearly a week producing

spectacular fireworks.

The moon, on the other

hand, is a good example of a

body having much of the

earth's gravity. The moon, the

only satellite of the earth, is

smaller than a few prominent

satellites of Jupiter. In mass, 80

moons are equal to the earth.

The moon's gravitational pull

is one-sixth of the earth's

force. That means, if you can

jump four feet high on the

earth, you can easily jump

24 feet on the moon because

your weight will be reduced by

one-sixth. Likewise, any person

weighing 66 kg. can have it

reduced to 22 kg. on Mars

because the gravity of Mars is

one-third of the earth's gravity.

The law of gravity can perform

many such wonders.

Astronomers have so far

discovered sixty satellites of

seven major planets. All of

them are bound to their

respective planets by gravity

and travel together in the solar

system.

A powerful telescope shows

the second giant, Saturn as an

extremely beautiful planet

adorned with the most colourful

and complex system of many

rings. Each ring consists of

millions of tiny bodies circling

as satellites under the spell of

the primary body. These are

thought to be remnants of a

satellite that strayed too near

and was disintegrated by

Saturn's power.

Stars

Do you know that the little

twinkling star is in reality a

massive globe of extremely hot,

glowing gases? Newton's law

plays the pivotal role in the

birth of such a star. Within a

large nebula—a large cloud of

distant stars, big particles whirl

together and go on accumu-

lating more and more particles

by mutual gravitation. In course

of time, the collection of

particles enlarges into a gigantic

ball of gas. As the particles

65

inside get compressed, the

pressure mounts and the

internal temperature rises. At

one stage the gas ball begins to

glow, and lo, a star is born!

In the formation of various

star systems, the gravitational

force has its role to play. If

you can get hold of a tele-

scope you can see some

unusual phenomena in the

stellar system. Some stars,

which appear single to naked

eye, will be really twins. They

will be turning round a

common centre of gravity.

Such pairs are known in

astronomy as binaries. There

are plenty of them in space.

Sometimes three or four stars

come together owing to mutual

gravitational pull. In rare cases

these triplets and quadruplets

will have another distant com-

panion which may again be a

binary. This makes a system of

fives and sixes. The most

surprising aspect is that the

distance between the stars in

each system will be millions of

kilometres. In some areas

bigger star groups of hundreds

and thousands called star

clusters, or stellar associations,

have been discovered by star-

gazers. The members of all

these systems share a common

origin and motion, and like

puppets, they are manipulated

by the star performer, gravity,

from behind the screen.

Finally, the force of gravity

hastens the death of a star.

The normal life span of an

ordinary star like our sun is

estimated to be 10,000 million

years. There are stars that live

longer up to 10,000,000

million years. But all stars

eventually die. How do they

meet their end? Hydrogen is

the main fuel that a star

converts into energy through

nuclear fusion and radiates as

light and heat. This energy

source will be used up in

millions of years depending on

its mass, and then a star

collapses; its internal gravitation

shrinks, like a deflated balloon.

It slowly loses its heat and

luminosity, for reasons of its

becoming denser and heavier.

Its mass will be much more

than that of the solar mass. In

the last stage the star's gravity

66

grows so strong that not even

light is allowed to escape. The

star's existence in its native

world will not be visible

because it will become dark

and cold. This 'ghost' of an

erstwhile bright star is termed

as a black hole. No doubt it

sounds incredible that a

luminous star would have such

a tragic end.

An Indian scientist made an

extensive study of black holes

and discovered that stars of

varying masses will have

different kinds of end. His

name was Dr. Subrahamanyan

Chandrasekhar (1910-1995),

who was born in Lahore and

became a world-renowned

physicist. He won the

prestigious Nobel Prize for

Physics in 1983.

Thus you see the whole

universe is the playfield of the

great miracle performer called

the Law of Universal

Gravitation, and like a genie, it

Star cluster

has been performing its tricks

for long ages and will-continue

to do so.

67

6 ROOTING FOR RADAR

Thick fog swirls around the

aircraft as it circles in the dark

night sky. Visibility is almost

zero. It is the worst kind of

weather to be flying in. The

runway of the international

airport is somewhere below the

aircraft, very close, the pilot

knows, but he is not able to

see a thing.

"Our time has come, my

dear," whispers an old woman

to her granddaughter. "Start

praying." The other passengers

look at each other, worried.

Would they reach home safely

that night?

But let us take a peek into

the cockpit to see how the

flight crew is handling the

crisis. Are they discussing strat-

egies, poring over flight maps,

calculating their positions, and

generally getting more and

more flustered? Surprise,

surprise! Inside the cockpit

there is peace and calm. And

smiles, as the radio crackles

into life. It is the engineer at

the airport control tower

calling, and with his precise

instructions, the pilot and the

co-pilot manoeuvre the plane

expertly into a near-perfect

landing. The crisis is over.

Bravo for the flight engineer,

did you say? Wait! How did

the engineer in the control

68

tower give the pilot his

instructions when he himself

could not see where the plane

was? Remember there was

thick fog all over!

A mystery? Hardly. The

engineer could do what he did

because he had a friend to

help him, a friend called Radar.

Satellite-tracking radar

a monkey!" Your voice or the

sound waves produced by it,

travelled to the farthest wall of

the cave, and were 'reflected'

back at you.

A radar is a system that

works on the same principle. It

is a system designed to send

out or transmit waves. If the

waves hit an object, they will

be reflected and will come

straight back to the radar.

When the radar receives the

echo, it realizes that there is

some kind of object, or

obstruction, in the path of the

wave. It really does not matter

69

Tracking

Radar is actually an acronym.

It stands for RAdio Detection

And Ranging. Terribly tech-

nical? Let us stick to calling it

Radar—it is simpler.

Do you remember when you

went on that trip to the cave

with your friends? When you

yelled, "You are a monkey!"

and heard the echo, "You are

Radar was developed nearly at the same time but independ-ently in the United States, England, Germany and France during the 1930s under various names, such as radio detection and radio location. In 1942, the US Navy coined the term 'radar' which became universal in all later applications.

1. Airport radar 2. Radar reception

if it is day or night; the radar,

like Superman, can 'see' just as

clearly either way.

Can you think of something

in nature that uses quite the

same technique to find its way

around? That is right—bats!

You must have heard the

expression 'as blind as a bat'

Did you ever wonder why

nature made bats which have

poor eyesights nocturnal

creatures? It is difficult for even

humans with good eyesight to

see in the dark; how in the

world do flying bats do it?

By the same principle of

sending out sounds and receiv-

ing echoes after they have hit

an obstacle. The method is

technically called echolocation.

Echolocation helps the bat

avoid obstacles, negotiate turns

and twists in a winding cave,

and home in on bugs and fruits.

Do you begin to see the

tremendous possibilities this

kind of system opens up?

Consider this. An enemy plane

is making its way to an inter-

national airport in India, under

the cover of darkness. Its

mission? To photograph the

airport from all angles, to study

its layout, and to take this

sensitive information back to its

government. All this information

will help the enemy country to

70

plan and launch a future attack!

At the control tower in the

airport that night, the mood is

relaxed. No planes are expected

for the next forty-five minutes

and the engineers are enjoying

well-deserved cups of hot

coffee. One of them, glancing

casually over the circular radar

screen, notices something

unusual—a blip—a bright spot

of light moving towards the

centre. The blip, he knows,

indicates an object the radar

has spotted. The centre of the

radar screen represents the

airport. Whatever the object be,

it is moving towards the

airport! The sophisticated radar

system in the airport can even

tell the engineer what the

object is—it is a plane.

Perhaps some pilot is in

trouble, the engineer reasons.

Maybe some plane has run out

of fuel and wants to touch

down and refuel. He gets on

the radio and tries to establish

contact with the pilot of the

unidentified plane.

"Control tower calling. Come

in, Captain."

There is no response. Surely

there is something wrong? The

control tower makes a few

important phone calls. All the

powerful ground lamps in the

airport are turned on, and

faced straight up towards the

sky. They are meant to help

the pilot and probably spot

him, but they have helped foil

the intruder as well! For if he

flies low enough to be able to

take photographs, he will also

be exposed! Radar has saved

the day!

Concepts

It is all very well to talk

about enemy planes and

control towers, you must be

saying, but how exactly does a

radar work?

As we have already dis-

cussed, the radar works on the

principle of echoes. Does that

mean that the radar is a noisy

contraption that keeps shouting

out cheeky messages that are

echoed back to it? Not at all.

To put it simply, a radar echo

is not 'listened to', it is made

visible as a spot of light in a

71

cathode ray tube which is quite

similar to an ordinary television

tube. Now do not let those

unfamiliar words confound you.

It is quite simple, really.

When you fling a stone into

a pond or a pool, you see

ripples spreading out from the

point at which the stone

entered the water. The ripples

are an example of radiation,

which simply means 'spreading

out in all directions from a

central point'. The waves that

radars transmit do the same

thing. They start off, or origin-

ate, at a certain point and

proceed in all directions.

Usually, waves need a medium,

a substance through which they

can travel. The medium for the

ripples in the pond was water,

but waves of the radar could

travel through media as diverse

as wood, water or air.

There is a special kind of

radiation called electromagnetic

radiation. What makes it so

special? This radiation can

travel through vacuum, that is,

in empty space, where there is

no air! In other words, electro-

magnetic radiation does not

need a medium to travel in.

Incidentally, you can thank

your stars that light waves are

also electromagnetic waves. If

they were not, light from the

sun would never have reached

us through all that vacuum

between the sun and the earth!

To come back to radio

waves, the waves that radars

transmit—these waves are also

electromagnetic waves. This

/ — — - — — \

It was the German physicist Heinrich Hertz (1857-1894) who artifically produced waves of different lengths from those of visible light. His discovery of electromagnetic waves led, in time, to the development of radio, television, and, finally, radar.

v. /

Water ripples—a movement of energy similar to that produced by electrical fluctuation which generates an electromagnetic wave disturbance.

ability to travel through vacuum cannot. Also, radio waves travel

is the biggest advantage they farther and much, much faster

have over sound waves, which than sound waves in air.

Sound waves and water waves— A. In sound waves molecules vibrate in the same direction as the wave train B. In water waves molecules vibrate

at right angles to the wave train

\ \Sarrie direction as Vspi\latWi\Af molecules

73

A

B

They travel, in fact, at

300,000 km.per sec. Try and

top that!

One of the most important

parts of a radar is, inevitably,

its transmitter. This device not

only transmits the radio waves

but is also responsible for

producing them. The waves are

sent out in short bursts, or

pulses, not in one continuous

stream. The intervals between

the pulses are very long when

compared to the length of the

pulse. For example, if the pulse

lasts for one second, the

interval will last for about

10,000 seconds! Of course, in

the real situation, both the

pulse and the interval last only

for tiny fractions of a second.

Why do you suppose there is

an interval at all between

pulses? Why can they not be

sent out constantly? Any

guesses? No? Read on.

When you shout in a cave, it

takes time for the sound to

travel to the cave wall, bounce

off it, and come back to hit

your ear-drums. Similarly, it

takes time for the radio waves

to travel to the object (if at all

there is an object), bounce off

it, and travel back. The inter-

vals between the pulses are to

receive the returning echoes, if

any. Get it?

The time taken for the

echoes to come back is meas-

ured automatically by the radar.

This helps it to calculate just

how far the object is from the

radar station. For example, if

you had to go up to your

friend's house, touch it and

walk right back, and if you

were walking at a speed of

two kilometres an hour and if

you came back home in half an

hour, it would be very easy to

calculate just how far your

friend lives from you. Obviously,

he lives half a kilometre away!

Similarly, knowing the speed at

which radio waves travel

(300,000 km. per sec.) and

knowing the time taken for the

waves to come back after

hitting the object, anyone could

calculate how far away the

object is!

So the wonderful radar not

only helps you to 'detect' the

presence of object, it can tell

you at what distance the object

74

is. This is called ranging. Do

you see now how appropriate

the name—RAdio Detection

and Ranging—is?

The wonders of the radar do

not stop at that! The radar can

also tell you whether the object

is moving towards the station

or away from the station. How

does it do this?

Frcqucncy

Imagine you are standing on

the pavement, waiting to cross

the road. Surely, this is some-

thing you do every day.

Imagine the road turns sharply

a few metres away, so you

cannot see the vehicles coming

towards you. You can hear

them, and you use your own

judgement to decide when it is

safe to cross.

Imagine you hear the toot of

a bus horn. It sounds too close.

You decide to wait till the bus

passes you. The driver keeps

his finger on the horn, in that

irritating way some people

have. Soon the bus has passed,

peace reigns again, and you

cross the road.

Did you notice something?

The pitch of the horn became

higher and higher as the bus

came towards you and dropped

suddenly as it passed you. This

is called Doppler effect (as

mentioned in Chapter 3).

Scientists would call the

increase in pitch as the bus

approached, an increase in the

frequency of the sound wave.

When the bus passed you,

Doppler effect

there was a sudden drop in

frequency.

A simple way to explain is to

understand the meaning of the

word. Another word for

frequency, not strictly in the

dictionary, could be 'oftenness'

The frequency of something

is how often that something

happens in a particular period

of time. If you have a pendu-

lum clock at home, notice how

the pendulum swings to and

fro, to and fro. If you measure

it accurately, you will see that

the pendulum swings exactly

once every second. You could

say that the frequency of the

pendulum is one swing or

oscillation per second, or sixty

oscillations a minute.

Waves—radio waves, sound

waves, sea waves—each has a

highest point and a lowest

point, like the swinging

pendulum has a leftmost point

and a rightmost point. Each

journey of the wave from its

highest to its lowest point is its

oscillation. The number of

oscillations of a wave per

second is called its frequency.

'But why are we talking

about frequency and oscilla-

tions? I thought we were

talking about radar,' did you

say? We are talking about

frequency because it is this

particular aspect of the radio

wave that the radar uses to

determine whether an object is

approaching or receding. How

does it work?

The frequency of the

transmitted signal is recorded

by the radar. When the echo

returns, its frequency is also

recorded and compared to the

recorded frequency of the

signal. If the frequency of the

echo is higher, the object is

coming closer (remember the

bus horn?) and if it is less,

the object is moving away.

Simple, isn't it? With the same

76

Radar echoes, or reflected radio waves, have been used to study thunderstorms and hurricanes. The radio waves used in these studies are reflected from large rain drops, hailstones, and ice crystals. Such waves are used to locate and follow the precipitation regions moving within clouds.

technique, the radar can also

tell you at what speed the

object is moving!

And how do you know where

the object is? Behind you,

ahead of you, to the right of

you, to the left of you? You

should be able to guess how it

is done!

The radar's transmiter is

constantly rotating, and its

rotation can be observed

constantly on a circular screen

called the Plan Position

Indicator (PPI). The centre of

the circle is the radar station.

Concentric circles are marked

out at different distances from

this centre. These represent

different distances from the

radar station. A bright line

called the trace sweeps round

and round the screen,

constantly, at the same pace as

the transmitter. Bright spots

called blips appear on the trace

from time to time. These are

produced by echoes returning

to the station. The trace moves

on but the blips stay in place

for some time before they fade

away. Looking at the blips on

the screen, you know which

direction the echo came from.

The object is obviously in the

same direction! Depending on

which circle they are closest to,

it is also possible to decide

approximately how far away

the object is. That is how the

system works.

And the shape of the object?

How big, how small, metallic,

non-metallic? Surely, the radar

cannot tell us that as well? But

it can! The strength of the

radar echo is stronger when it

hits metal and when it hits

larger objects!

So what does a radar tell

you, in the end? It tells you of

the presence of an object; how

far it is; where it is; how big it

is; what material it is made of

and whether it is coming

towards you or going away

from you. There is only one

word for it—amazing!

During war

I bet you are bursting to ask

me something. Who invented

it? Well, all you quiz buffs who

quickly stash away information

77

like this in some pigeon-hole in

your brains are going to be

disappointed. For there was not

just one single person who

thought up and devised this

wonderful mechanism. It was a

gradual thing, with scientists

from all over the world adding

a bit of this and a little of that

to give us radar as we know it

today.

What really triggered off and

hastened its development was

the outbreak of the second

world war. Vital locations were

being bombed on both sides.

Desperate measures were

needed to combat the twin

terrors from the skies—enemy

aircraft and deadly missiles!

Scientists were pressed to the

task, and they did make an

epochal success of it!

Since then, radar has got

more and more sophisticated.

You have now missiles with

small radars built into them

that are used for offence, not

defence. The built-in radar can

'home in', or converge accur-

ately on a moving target! The

target may swerve and change

direction, or run circles around

the missiles, but the missiles

will detect the change in

direction and follow, relentless,

ruthless. Until...WHAM! Maybe

our forefathers foresaw this.

That is probably where they

got their idea of the

Sudarshana Chakra from!

But there are ways to hood-

wink the best of detectors,

loopholes in the strictest of laws.

The Stealth Bomber, the

pride of the US aviation

industry, is built in such a

fashion as to escape notice by

even the most sophisticated

radar. The Stealth, dark and

sleek and streamlined, is quite

enough to strike terror into any

radar engineer's heart. Only

until the human mind comes

up with an ultra-radar that can

even detect the Stealth!

Okay, so we have only been

talking war and bombs and

missiles and killing in con-

nection with the radar.

Does that mean that the

radar personnel just sit around

and twiddle their thumbs when

there is no war on? Certainly

not, for there are many other

uses of the radar.

78

Use of radar in controlling aircraft traffic

Peaceful uses

We have already talked about

how the radar is vital in

directing planes to a safe

landing in bad weather. This is

called ground-controlled

approach radar. A different

kind of radar called the traffic-

control radar is used to control

the landing and taking off of

planes in busy international

airports. Aeroplanes also use

radar altimeters, which tell

them how much they are from

the ground.

Ships on the high seas also

use radar to warn them of

icebergs, shorelines and other

obstacles in their path. A kind

of traffic-control radar is also

used at busy harbours to direct

the comings and goings of

ships. Radars are used at very

busy intersections on the road!

Weather forecasting has

taken a giant leap forward with

the help of the radar. The

radar can detect and track

storm centres and give advance

warning of hurricanes, torna-

does and squalls so that people

can be evacuated in good time

if necessary. In space science,

the radar tracks satellites on

their journey around the earth.

It has helped scientists in

getting information about the

79

solar system. Radar signals

beamed to the moon have

come back loaded with data

about the moon's pockmarked,

uneven surface. This knowledge

was instrumental in the success

of the Apollo-manned flight to

the moon (remember Neil

Armstrong and Edwin Aldrin?).

Bowled over by the power of

the radar? The funny part is

that although it is hardly fifty

years since it was first

developed, today it is difficult

to imagine a world without it!

And now that you are much

informed about the radar, just

go out there and proceed to

astound your friends with

your genius!

7 LEVER POWER

My brother Raju is very

strong. He can move big

stones. He can make rocks fly.

He can clear a height of ten

feet when he jumps. He can

do many things which you and

I think impossible.

Do you want to see how

strong Raju is? Come with me.

Here is a big stone. Part of it

is under the ground. I try to

move it but I cannot. I bring a

dozen friends to move it. Yet

the stone does not move. I call

Raju. He examines the stone

and says, "Why not? Bring me

a crowbar and a brick or a

small stone."

I do his bidding. He places

the brick close to the big

stone. He rests the crowbar on

the brick. He pushes one end

of the crowbar between the

stone and the ground. The free

end is longer than the end

which rests between the brick

and the stone.

Raju presses the free end of

the crowbar with all his

strength. The big stone quivers.

Then it slowly moves up,

comes out of the ground, and

turns over.

A friend

Raju smiles and says, "I can

move anything. Even the earth,

if I have a long enough

81

crowbar. I owe my strength to

my friend, the lever. Yes, I

used lever power."

Raju looks at a branch of a

mango tree. He asks, "Do you

want to see the big stone fly?"

I shout, "Don't try to fool us.

You can't make the stone fly."

Raju brings a big, broad

plank of wood. He rests it on

a stone. He moves the big

stone on to the end of the

plank which rests on the

ground. The other end tilts up.

Raju climbs up the tree. He

stands on a branch of the tree

and asks us to move away.

"Keep well away, boys.

Otherwise the stone may fly

and crash on your heads." We

run to safety.

Raju jumps down. He lands

on the free end of the plank

making it move down under

the force. The other end, on

which the big stone rests,

springs up. The big stone flies

into the air, makes an arc and

lands with a thud, a little

distance away.

"That is a flying missile," I

shout.

Raju says, "Ah, that is

nothing but my friend lever at

work. Every circus artiste

knows it.

"There are many tricks they

perform, many of which

depend on lever power. I will

tell you of one such act. You

must have seen it. A chair is

held up at a height of three to

four metres. Some distance

away, a little girl stands on one

end of a plank fixed over a

roller. The other end is up in

the air. Close to this end is a

ladder. It looks like an inverted

'V', with enough space on the

top for a man to stand.

"An artiste moves up the

ladder to the top and waits.

The band rolls; the signal is

given. The man on the ladder

jumps and lands on the free

end of the plank. It goes down,

and the end of the plank

where the girl is standing

swings up under the force. The

girl flies through the air and

lands on the chair. It rocks a

bit with the impact. The men

holding the chair bring it down.

The crowd applauds. The girl

gets all the credit..." Raju

pauses.

"You mean nobody gives any

credit to lever power," I say.

"Right," Raju grins.

"I can jump over the wall,"

Raju points to a portion of an

old wall. It is about ten feet

high.

"You can't," we shout.

Raju says, "Wait and see."

He moves off and returns

with a long bamboo pole. He

holds the pole parallel to the

ground and begins to run

towards the wall. Faster, faster.

He is just two feet from the

wall. Then one end of the pole

hits the ground. Raju flies up,

along with the other end of the

pole. He lets go the pole and

flies over the wall, landing on

the other side.

We wait for him to come

back. We cheer him. I tell him,

"I know, your friend lever did it

for you. And it is known as

pole vault."

"Yes. It is part of athletic

events. It finds a place even in

Olympics. The athlete has to

clear a crossbar. The height of

the crossbar is raised with

every successive jump. The

height the athlete clears, with-

out touching the crossbar, is

credited to him. Lever power

makes pole vaulting possible,"

Raju says.

"How?" I ask.

83

"The pole used by the

athlete is normally 4m. to 5m.

long and supple," Raju says.

"A bamboo pole is used by

many pole vaulters. There are

poles made of fibre glass also.

Holding the pole the athlete

runs towards the crossbar. Faster

and faster he runs till he is

close to the crossbar. He drives

the pole into a box on the

ground, below the crossbar.

The forward speed is checked

and transformed into a mighty

force. It pushes the free end of

the pole upwards. The athlete

swings up with the pole. Then

he lets go of the pole and goes

over the crossbar, feet up. He

arches his body to get extra

clearance, landing on sand or

an inflated mattress," Raju

explains.

Inclined plane

We hear mother calling.

There is a car in front of the

main door. Uncle Bharatan has

come. We are happy. He tells

us, "I don't know how to get

this big suitcase up the steps to

the verandah. Of course, the

suitcase has wheels. But wheels

are of no use when one has to

take it up the steps."

Raju smiles. He brings a

plank of wood and places it so

84

that one of its ends rests on

the ground and the other

touches the edge of the

verandah. He says, "This is an

inclined plane. My friend lever

will help me here too." He

rolls the suitcase up the slope

on to the verandah. We are

thrilled. Uncle Bharatan is

pleased.

"You seem to know a lot

about levers." Uncle grins at

us. "I will tell you a story."

"Please, Uncle."

"It is a real incident that

happened centuries ago. Raja

Raja Chola was a great ruler.

He ruled from Thanjavur,"

Uncle Bharatan begins.

"The King wanted to erect a

temple for Lord Brihadeswara.

He laid down a condition—the

temple should never cast a

shadow. He also wanted the

roof to be made of a single

stone.

"The experts sat together.

They knew about the earth's

path round the sun. They also

knew about earth's rotation

round an imaginary axis. They

made several calculations and

made models.

"Finally they were able to

make a model for the temple.

This model did not cast a

shadow all through the year.

The experts were happy," says

Uncle Bharatan.

"Now there remained the

other problem. The people

knew it was easy to get a

single, big stone cut out from

the hills nearby. But how would

they get it to the top? This

posed a problem. Such a big

stone could not be lifted up.

No rope would stand the

weight. Not enough men could

get on to the top of the

structure to pull the stone up.

"For days, the experts saw

85

no way out. Suddenly, one of

them came up with an idea. It

was quite simple. A long road

had to be laid, all the way

from the foot of the hills up to

the top of the temple. The

slope had to be gradual so that

it would be easy to drag the

stone along the slope all the

way to the top. It was a

brilliant plan. The experts

reported to Raja Raja Chola.

The ruler agreed.

"The construction of the

temple began. Thousands of

masons, carpenters and coolies

worked at the site. Thousands

of stone cutters worked at the

hills. One group worked on the

stone for the roof. They chose

the right block of rock and

started work. The road too was

laid.

"The people then tied ropes

round the stone. A dozen

elephants were brought to pull

the ropes. It was hard work

and it was several days before

the stone could reach the top.

Then the men pushed the

stone to rest it on the pillars,"

Uncle Bharatan concluded.

"The inclined plane made it

possible," I remark.

"Right. Do you know it is

easier to take a heavy weight

along an inclined plane than to

lift things straight up because

gravity exerts a downward force

on all objects. But when you

take a heavy object up an

inclined plane, it loses its

weight," Uncle says.

"Impossible," I cry.

"Listen, my boy. Suppose

you have an even slope and it

rises one foot when you go ten

feet along the slope. This is

called the gradient. It is called

a gradient of one in ten. This

slope makes every object ten

times lighter. A load of ten

tonnes on the gradient will

move with force enough to

move a load of one ton. The

rule is simple: the lesser the

inclination of the plane, the

lesser the force needed to push

an object," Uncle explains.

"Does the inclined plane use

lever power?" I ask.

"Yes, remember the defini-

tion of a lever—it provides

mechanical advantage. That is

what the inclined plane does,"

says Uncle.

86

Pulley

A little later Uncle Bharatan

wants to take a bath. He wants

water to be brought up to the

bathroom. I reach for the pail.

Raju stops me. He fixes a

pulley with the help of two

steel hooks against the

verandah on the first floor. He

loops a rope round the pulley

and ties one end to the bucket.

The other end is in his hand.

Then he tells us to fill the

bucket with water and he pulls

the bucket up. Soon the bucket

is within Raju's reach. He leans

forward, grabs the bucket of

water, takes it to the bathroom

and empties the water into the

tub. He does it a dozen times.

Then he runs down, saying,

"Thank my friend, the pulley. I

mean, my friend, lever. For the

pulley also works by lever

power."

Uncle Bharatan overhears

Raju. "Lever gives us power.

Power to move heavy objects,

to drag heavy weights^ to raise

heavy loads," he says.

"Can you move everything?"

I ask.

"Yes. Archimedes..."

"Archimedes! I know who he

was. I have read about him," I

87

interrupt Uncle Bharatan. "He

was a famous scientist."

"Once Archimedes went to

meet King Heiro," continues

Uncle Bharatan. "He told the

King, 'You may not believe it,

but I can move anything. Give

me a place to stand. I will then

move the world.'

"'I believe you, my friend,'

the King said. But show me

how you can move heavy

objects. There is a ship. It is a

three-master merchant man. I

shall get it on shore. I shall

load it. I shall ask a few men

to be on board the ship. Thus,

I shall make the ship really

heavy. Can you move the ship

over the sand?' Archimedes

nodded."

"What happened, then?" I

enquire.

"The King instructed his men

to bring the ship ashore.

Archimedes made the necessary

preparations. He fixed strong,

stout poles in the sand. Then

he brought a few pulleys and

thick ropes and fixed them on

the poles. One end of the rope

was hooked to the ship. The

free end was looped over one

pulley, over the next, till the

rope ran round all the pulleys.

The rope's free end was left

hanging.

"Archimedes was ready to

move the ship. The news

spread. Thousands of people

came to watch the miracle.

The King took his seat on a

special rostrum. After greeting

the King, Archimedes picked

up the free end of the rope.

He pulled lightly. The ship

moved easily. It seemed to glide

over the sand. Archimedes

proved that he could move the

ship, loaded with cargo and

men. Yet, it had taken

hundreds of men many days to

get the ship out of the water.

"The King said, 'I am proud

of you, my friend. You moved

the ship, all by yourself.'

Archimedes replied, 'I only

made the levers work for me.'

So, lever power is nothing

new, my boys," declares Uncle

Bharatan.

Mother comes in with a tray

with bottles of cold drinks.

There is a bottle opener on the

tray, too. She extends the tray

towards Uncle. "Come,

88

Bhaiyya, you must be thirsty,"

she says.

Uncle says, "Cold drinks are

always welcome." He picks up

a bottle and uses the bottle

opener to remove its cap.

"That was lever at work,"

Uncle tells us. "I applied

pressure upwards on the free

end of the opener and the cap

came off." Then he hands us a

bottle each. We run out into

the open leaving the adults to

their talk.

Balance

"Do you want to see some

magic?" asks Raju. We nod. He

places a plank of wood on a

small stone. He places it so

that the ends are unequal. He

puts a big stone at the smaller

end. "Now, I can make a see-

saw. The plank won't touch the

ground," says Raju, while he

places a small stone at the

longer end. He adds a few

more small stones. Finally the

plank moves up. It balances,

even though the weights at the

two ends are unequal. Raju

turns to us and says, "That,

again, is lever at work.

"It is this principle that is

used in the common balance.

The one that shopkeepers use

to weigh things. When the top

beam of the balance is held at

the centre, the length of the

arms is the same on either

side. So we can weigh things.

Suppose, you want a kilogram

of sugar. The shopkeeper puts

the weight on one of the pans.

He fills a packet with sugar

and places it on the other pan.

He watches the beam. He

takes off some sugar if the

beam dips towards the pan

holding the sugar. Or he adds

more sugar if the pan holding

the weight dips. Soon the

beam does not dip towards

either side. Then the shop-

keeper knows the packet holds

a kilogram of sugar," says Raju.

"The shopkeeper sometimes

cheats on the weight. Lever

helps him in this," adds Raju.

"How?" I ask.

"He uses a balance in which

the arms are not equal. The

difference is very slight, and is

not noticeable. He puts the

89

weight on the pan with the

shorter arm. The item to be

weighed is put on the pan with

the longer arm. When the

balance is at equilibrium, the

item that is weighed is a little

less than the weight against

which it is weighed. Thus he

cheats on every weighing,"

Raju says.

"So lever power is his...what

do you call someone who helps

a criminal?" I cannot remem-

ber the word.

"Accomplice," Raju beams

happily.

He asks us whether we can

explain how the lever works.

We cannot.

common balance and the

crowbar.

"In the second order lever,

B

Orders

Raju explains. "A lever is a

simple machine, a beam or a

rod supported at a point called

the fulcrum and used to move

heavy loads.

"There are three types of

levers. In the first order lever,

the fulcrum lies between the

load and the effort (or force).

Some examples of this kind of

levers include the see-saw, the

A. First order lever B. Second order lever C. Third order lever

Fulcrum

Fulcrum

Fulcrum

Force Load

90

Force

A

Force | Load

Load

C

the load lies between the effort

and the fulcrum as in the case

of a wheelbarrow and the

bottle opener.

"In the third order lever, the

effort lies between the load and

the fulcrum. Examples of this

kind of lever include the

broom, the fishing rod and the

sugar tongs.

"You can combine a pair of

levers to produce double levers.

The pliers and scissors are

instances of double lever of the

first order; the nutcracker of

double lever of the second

order; and tweezers of double

lever of the third order.

"The lever is at work

everywhere. See the tree. Its

branches are swinging in the

breeze. The wind is applying

pressure. The pressure is taken

on by the fulcrum of the tree,

its base. It is taken in by the

power that lies in the roots.

Yes, the tree stands and

survives strong winds owing to

the lever principle. When too

much pressure is applied by the

wind, as when hurricane

strikes, supple trees bend. Thus

they reduce the amount of

pressure. The big trees get the

pressure shifted to the base

and thence to the roots. And,

at times, the roots do not have

enough strength to withstand

the pressure. Then the tree is

uprooted."

Lever is the basis of all

machines. It is our friend.

8 AUTOBIOGRAPHY OF AN ATOM

I am so small that you cannot

see me even through a powerful

microscope. In fact, I live in such

close proximity with millions of

my friends that it is almost

impossible for you to separate

me from the rest. If one hundred

million of us stand in a queue

touching each other, the queue

will be just one centimetre long.

'Atomos'

I am writing my story briefly.

Democritus believed, 'to under-

stand the very large, you must

understand the very small'.

Democritus was a Greek philo-

sopher who lived in 400 B . C . He

said everything that exists is

made up of tiny particles packed

closely together. He called these

particles 'atomos' which is a

Greek word for 'indivisible'. Thus

I came to be known as atom.

Another Greek philosospher

called Aristotle (384-322 B . C . ) pooh-poohed Democritus'

theory. He said that everything

was made of four elements—fire,

water, earth and air.

My potentialities remained

dormant for a long time. It was

2,000 years after Aristotle that

scientists resumed their research

on me. Galileo Galilei (1564-

1642), astronomer and physicist,

refuted Aristotle's theory and laid

stress on tests and experiments.

92

Also important at this time was

the scientific use of microscope.

Robert Boyle (1627-1691),

British physician and chemist,

combined the ideas of Aristotle

and the alchemists, those who

tried to change baser metals into

gold or silver (See box on

page 98). Boyle realized that

certain kinds of matter cannot be

made by combining others while

some can be. There are certain

materials which could be broken

down into simpler substances.

Thus he concluded that

everything on earth must be made

of a limited number of simple

substances—elements in Greek.

Theory

More and more elements were

discovered. Robert Boyle

discovered phosphorous, gold,

and silver. Hydrogen and oxygen

together make water which is a

liquid.

Another interesting fact was

hydrogen and oxygen always

joined together in exactly the

same proportion. It applied to all

the combinations. At the same

John Dalton

time when some elements were

mixed the scientists got nothing.

I am recognized by the

element to which I belong. An

English chemist and physicist,

John Dalton (1766-1844),

studied how elements combine in

more than one set of pro-

portions. For example, 12 gms.

of carbon combine with 16 gms.

of oxygen to form carbon

monoxide. It is a poisonous gas,

which is a major air pollutant

emitted by the vehicles on the

road. It not only causes respir-

atory problems but results in

physical and mental impairment.

Carbon dioxide, a gas which is

used to put out fires rapidly, is a

93

combination of 12 gms. of

carbon and 32 gms. of oxygen.

This gas is not readily dissipated.

It hangs around and affects the

climate of the world. As a result,

scientists predict a trend of

global warming which will melt

the polar ice caps thus flooding

the coastal cities.

Dalton explained that crystals

of gold always looked alike and

so also crystals of copper but

crystals of gold and copper

together never looked alike.

Thus, he concluded that all

elements are made of us, the

atoms, and that we of the same

elements are identical in size,

shape and mass. Also, elements

combine in more than one set of

proportions. For instance, when

hydrogen and water combine to

form water, two atoms of hydro-

gen combine with one atom of

oxygen. Each oxygen atom is

eight times as heavy as each

hydrogen atom. Therefore,

Dalton is called the originator of

modern atomic theory. He said

all matter is made up of very

minute particles which cannot be

further subdivided and I am that

small particle, the atom.

Electrons

Dalton's atomic theory is an

important milestone in the

history of science because of its

emphasis on our weight, the

atomic weight. Atomic weight is

the sum of protons and neutrons

in my nucleus and atomic

number is the number of protons

in my nucleus.

Everybody thought that I am

the smallest particle but there is

something else smaller than me

and that is my nucleus, the most

powerful part of my body.

Protons and neutrons constitute

my nucleus while electrons are

present outside the nucleus.

Although, in the beginning, I

was considered invisible, indivis-

ible and indestructible, I was

subjected to all sorts of trials and

tribulations in the name of

experiment in the laboratories of

scientists. In 1875, Sir William

Crookes, a British scientist,

imprisoned a few of us in a

narrow, dark tube with two

impenetrable walls at the two

ends called anode and cathode,

and subjected us to a high

voltage electric current. We

94

could not bear the shock and we

broke. Very small parts from our

bodies were extorted and forced

towards the anode.

Scientists could not understand

what these were. They were

called cathode rays. It was

established that they play a dual

role of both particles and waves.

At this stage, an English

physicist called Joseph John

Thomson (1856-1940), respect-

fully and affectionately called

Sir J .J . by his disciples, deflected

them from their straight path

from the cathode by placing the

tube in a magnetic field

perpendicular to their path.

From the nature of the deflection

he concluded that these are

negatively charged particles.

Joseph Stoney named them

'electrons' in 1891. So

Sir J.J . concluded that tiny

negatively charged particles

called electrons were responsible

for the conduction of electric

current.

Sir J .J . spared no effort to

determine the specific charge—

the ratio of the charge (e) to the

mass (m) of the electron. The

value is 1 .76x lO n coulombAg-

It was a remarkable feat and it

was commemorated by

constructing a huge building in

the honour of Sir J .J . And at the

top of this building the symbol

e/m stands as an epigraph. The

American scientist, Robert

Andrews Millikan pounced on

the electron and did not rest until

he determined the magnitude of

the charge on it. It is the smallest

possible charge and any charge

is an integral multiple of the

value of e. He found it to be

1.6xl0"10 coulomb. The quotient

of e and e/m gave the mass of

the electron as 9.1xl0~31kg.

which cannot be determined by

an ordinary balance.

Isotopes

Dalton was of the opinion that

the difference in atomic weight

accounted for the different

properties of different elements.

He was wrong because Francis

William Aston (1877-1945), an

English physicist, devised an

instrument called mass

spectrograph and separated

those of us belonaing to the

95

same element, according to our

weights and called us isotopes. In

other words, any of two or more

forms of us of an element having

the same or very closely related

chemical properties and the

same atomic numbers are called

isotopes. Hydrogen has three

isotopes of atomic weights 1, 2

and 3 called hydrogen, deuterium

and tritium respectively. Aston

was awarded the Nobel Prize in

1922 for his commendable work.

Dalton assigned a value 1 to

the weight of our hydrogen

friend. He is the lightest of us all.

Once hydrogen was used to fill

balloons. Since hydrogen is

highly inflammable, now helium

is used to fill balloons. Helium

was assigned the value 4, carbon

12, oxygen 16 and so on. This

means that our helium friend is

four times heavier than our

hydrogen friend and our carbon

friend 12 times heavier than

hydrogen. Dalton had no

sophisticated equipment to work

with; he arrived at his theory

purely on the basis of his

reasoning power.

A serious problem now startled

the scientists. How was it

Baron Ernest Rutherford

possible that I was neutral,

showing neither positive nor

negative charge, when I had the

negatively charged electrons

present in me? Scientists began

to seek a proper explanation of

the mystery behind me. They

wanted to go deep into my

interior.

Baron Ernest Rutherford

(1871-1937), a Britisher,

working in M.C. Gill University

in Montreal, was a voracious

reader and a good experimental

scientist.

One day in 1911, Rutherford

started hitting us resting in a

gold foil, using alpha particles as

bullets. Alpha particles are

positively charged particles

96

spontaneously emitted by radio-

active elements like radium. This

emission cannot be stopped by

any process. Some of the alpha

particles on passing through the

foil showed a small deviation

from their original straight path,

some a large deviation, some

actually bounced back.

Rutherford argued from these

results that my mass and positive

charge are concentrated in a

small region at my centre and he

called it nucleus. It is like your

heart, the most vital part of your

body. The net positive charge on

my nucleus is equal to the total

negative charge of all electrons

in me.

Rutherford compared me to

the solar system. If my nucleus is

the sun, the electrons are the

planets revolving round the sun.

Remember that my electron not

only revolves round the nucleus

but also spins like the earth

about its own axis. Thus my

electron is endowed with all the

qualities of the earth! Rutherford

glorified me. I am round like a

sphere with a diameter of 101 0m.

and my nucleus is tiny and has a

diameter of 1015 m.

Protons

I was at peace with myself for

nearly three years but Rutherford,

as energetic as the alpha particle

he used, was scheming adroitly

to conquer me further and to

extract more of my secrets. He

enclosed some of my nitrogen

friends in an evacuated chamber

and bombarded them with alpha

particles. He investigated into

the highly penetrating radiation

racing out of the chamber.

On a screen at a distance of

more than 40 cm. from the

chamber and covered with

fluorescent material like zinc

sulphide, he observed bright

spots. He ruled out that these

were due to the alpha particles

he used because they could not

have a range of more than

40 cm. So these bright spots,

scintillations as they were called,

puzzled him. He found to his

utter surprise that my nitrogen

friends in the chamber had been

converted into oxygen friends. It

was another glittering feather in

his cap.

Rutherford had achieved

artificial transmutation of

97

The apparatus with which Rutherford first observed artificial transmutation (atoms of some elements slowly change into atoms of other elements)

elements, in other words, con-

version of one element into

another. Rutherford succeeded

most unexpectedly in doing what

most alchemists failed to do (See

box below).

Further experiments revealed

to Rutherford that the penetrat-

ing radiation here consisted of

tiny particles which are the

nuclei of my hydrogen friends.

When the single electron in

hydrogen atom is removed, the

remaining nucleus is 'proton'.

Thus the hydrogen nucleus has

only one proton. So the

radiation in Rutherford's experi-

ment consisted of protons. Thus

the proton was discovered in

1914, nearly 17 years after the

discovery of the electron.

The proton has a positive

charge of the same magnitude as

that of an electron. Sir J .J .

determined its specific charge •

also and then showed that its

mass is 1,837 times that of an

electron (1.67xl0~27 kg.). In this

way Rutherford extorted another

constituent of my body, the

98

One of the oldest dreams of the alchemists of the Middle Ages was to change common metals into gold. With the trans-mutation of elements, modern science has now made it possible. However, commer-cially, it is not economical to produce gold in such a manner.

proton. So protons constitute my

positively charged nucleus.

There seems to be no limit to

research, for, as has been said

and truly well said, the more the

sphere of knowledge grows, the

larger becomes the surface of

contact with the unknown.

Scientists of those times who

followed Rutherford's work

carefully could not answer one

pertinent question they put to

themselves. Our helium friend

has a weight 4 with two protons

in its nucleus. So the mass of

helium nucleus is far greater than

the total mass of 2 protons. Why

is this difference? They ruminated

over it for long. However, the

charge carried by its two protons

equals the charge of helium

nucleus. How should this excess

weight be accounted for? The

scientists decided to struggle

hard to lift the veil hiding

something else in my nucleus.

Neutrons

In 1932, James Chadwick, an

English physicist, carefully

studied the experiments done by

Bothe and Becker before him in

which they bombarded a

beryllium target with alpha

particles. However, they could

not properly interpret the results

of their experiment. When the

same experiment was repeated

by Joliot-Curie—Jean Frederic

Joliot (1900-1958) and Irene

Curie(1897-1956)—a husband

and wife team, they found that

the radiation from the target

knocked off energetic protons

from paraffin which is rich in

hydrogen. But they also failed to

give a proper explanation.

Chadwick confirmed that the

radiation from the beryllium

target when allowed to pass

through paraffin gave protons.

He had learnt in high school that

when a perfectly elastic ball A

strikes an identical ball B which

is at rest, A comes to rest and B

is set into motion with the

velocity of A. He argued that a

similar process was taking place

in the beryllium experiment, too.

He said that the radiation from

beryllium must contain particles

similar to protons of paraffin and

that they must be uncharged or

neutral. The particles were called

neutrons.

99

The neutron immediately

solved the problem of the weight

of the helium atom's nucleus. It

contains two protons and two

neutrons and hence has a weight

of 4. So the nucleus contains not

only protons but also neutrons.

Likewise, a carbon atom of

weight 12 contains 6 protons,

6 neutrons and 6 revolving

electrons. With the discovery of

neutron, the list of building

blocks for constructing me is

complete. Neutrons act as a

buffer between protons in the

nucleus, easing the repulsive

forces experienced by two like-

charged protons. The single

proton in hydrogen does not

require any buffering. Protons

Neils Bohr

Dmitri Ivanovich Mendeleev

and neutrons in my nucleus are

jointly called nucleons.

Neils Bohr (1885-1962), a

Danish physicist, studied the

nature of light emitted by me

under different circumstances

and affirmed that electrons in me

revolve round my nucleus in

different shells. My picture is

complete. I have a nucleus con-

taining protons and neutrons at

my centre and electrons revolve

round the nucleus in elliptical

orbits. These electrons move in

definite, predetermined paths

and cannot orbit anywhere else.

We are all atoms belonging to

different elements. By 1850,

55 elements with different

o

e

o

Proton

Electron

Neutron

Oxygen

Hydrogen Helium

properties were known and there

was no apparent order in their

properties. An attempt was made

to bring order out of chaos. I

recall with admiration and

affection that great Russian

chemist, Dmitri Ivanovich

Mendeleev (1834-1907) who

arranged the elements in the

order of increasing atomic

numbers (See table on page

102). Here and there he put a

heavier element before a lighter

element to get elements with

similar properties in the same

row. For example, tellurium of

atomic weight 128 was ahead of

iodine of atomic weight 127.

Henry Moseley was dissatisfied

Lithium

with Mendeleev's work. He

studied the characteristics of

X-rays the nature of which

depends on the nature of the

target used to generate X-rays.

You know X-rays, discovered by

the German physicist, Wilhelm

Konrad Roentgen (1845-1923),

in 1895, as the radiation

produced when high-energy

electrons strike a tungsten target.

Moseley concluded that chemical

properties of an element do not

depend on atomic weight but

upon atomic number. This

number, as mentioned earlier, is

the number of revolving

electrons in me or the number of

protons in my nucleus. Uranium

101

Albert Einstein

friend of atomic weight 238 has

92 protons and 92 electrons.

Hence its atomic number is 92.

The atomic weight and atomic

number are represented by A

and Z, the first and the last

letters of the English alphabet.

Thus A and Z began to adore me

as my crown and foot-rest near

my throne. For example, my

sodium friend is shown as Na

because his atomic weight is 23

and atomic number 11. Na is the

symbol for sodium.

My mass is very very trivial. In

general, the atomic weight of

any element expressed in grams

contains 6.03xl02 3of us. This

number obtained by Amedeo

A=23 Z= l l

Avagadro (1776-1856), an

Italian chemist and physicist, and

named after him, is called

Avagadro's number. Therefore

both 23 gms. of sodium and

16 gms. of oxygen contain

6.03xl02 3 of us.

Fission

I am also a store-house of

energy. How? My nucleus

weighs slightly less than the total

weight of its constituent protons

and neutrons. Albert Einstein

(1879-1955), a Germany born,

American physicist, swept the

horizons and penetrated into the

infinitesimally minute. He put

forward a principle that mass

and energy are not entirely dif-

ferent physical quantities but

different manifestations of the

same essence. They are similar

in the sense that one can be

converted into an equivalent

amount of the other. If a mass

(m) disappears, it reappears in

the form of energy (E) and

Einstein gave the equation,

E=mc2 where 'c' is the velocity

of light in vacuum which is

102

Periodic Table

Hydrogen Titanium Technetium Gadolinium Astatine HI Ti 22 Tc 43 Gd 64 At 85

Helium Vanadium Ruthenium Terbium Radon He 2 V 23 Ru 44 Tb 65 Rn 86

Lithium Chromium Rh odium Dysprosium Francium Li 3 Cr 24 Rh 45 Dy 66 Fr 87

Berylium Manganese Palladium Holmium Radium Be 4 Mn 25 Pd 46 Ho 67 Ra 88

Boron Iron Silver Erbium Actinium B 5 Fe 26 Ag 47 Er 68 Ac 89

Carbon Cobalt Cadmium Thulium Thorium C 6 Co 27 Cd 48 Tm 69 Th 90

Nitrogen Nickel Indium Ytterbium Protactinium N 7 Ni 28 In 4ft Yb 70 Pa 91

Oxygen Copper Tin Lutetium Uranium O 8 Cu 29 Sn 50 Lu71 U 92

Flourine Zinc Antimony Hafnium Neptunium F 9 Zn 30 Sb 51 Hf 72 Np 93

Neon Gallium Tellurium Tantalum Plutonium Ne 10 Ga 31 Te 52 Ta 73 Pu 94

Sodium Germanium Iodine Tungsten Americium N a i l Ge 32 I 53 W 74 Am 95

Magnesium Arsenic Xenon Rhenium Curium Mg 12 As 33 Xe 54 Re 75 Cm 96

Aluminium Seienium Cesium Osmium Berkelium A1 13 Se 34 Cs 55 Os 76 Bk 97

Silicon Bromine Barium Iridium Californium Si 14 Br 35 Ba 56 Ir 77 Cf 98.

Phosphorus Krypton Lanthanum Platinum Einsteinium P15 Kr 36 La 57 Pt 78 E 99

Sulphur Rubidium Cerium Gold Fermium S 16 Rb 37 Ce 58 Au 79 Fm 100

Chlorine Strontium Praseodymium Mercury Mendelevium a 17 Sr 38 Pr 59 Hg 80 Mv 101

Argon Yttrium Neodymium Thallium Nobelium A 18 Y 39 Nd 60 Tl 81 No 102

Potassium Zirconium Promethium Lead Lawrencium K 19 Zr 40 Pm 61 Pb 82 Lw 103

Calcium Niobium Samarium Bismuth Ca 20 Nb 41 Sm 62 Bi 83

Scandium Molybdenum Europium Polonium Sc 21 Mo 42 Eu 63 Po 84

3x10s m. per sec. This is called

the binding energy of helium

nucleus and is expressed in

electron-volts (ev). The greater

the binding energy, the more

stable that nucleus is. My iron,

cobalt, nickel and other friends

are the happiest for this reason.

Now the scientist conceived a

strange idea. If a heavy nucleus

like that of uranium can be split,

it will produce smaller daughter

nuclei which are most stable and

consequently the splitting should

release lots and lots of energy.

The American physicist,

Enrico Fermi bombarded

uranium with neutrons to split it

into simple fragments. He failed

to interpret the results of his

work reasonably. German

chemists, Otto Hahn and Fritz

Strassman interpreted the results

correctly when they found in the

reaction products, barium,

lanthanium and cerium.

Uranium was split! But the sad

part of it is that for every

neutron used, a larger number of

neutrons are released when each

uranium nucleus is split. These in

turn bombard uranium nuclei

and this proceeds ad infinitum

and soon countless uranium

nuclei are split, releasing

uncontrollable energy. This was

achieved on December 2, 1942,

by Fermi, in America. Such a

large amount of energy released

in a split second causes only

destruction and cannot be used

for peaceful purposes.

Thus he paved the way to

make the atom bomb. The

"Little Boy" dropped on

Hiroshima and the "Fat-man"

dropped on Nagasaki literally

burnt Japan. The Japanese who

survived the nuclear holocaust

are still reeling from the

treacherous effects of radio-

active fallout.

Am I responsible for all this? A

knife in the hands of a surgeon

gives a new lease of life to a

patient but in the hands of a

murderer snaps off a life. I too

am neither good nor bad but it is

the purpose to which I am put

that can be either.

104

9 LOUIS PASTEUR

The world has produced

many geniuses whose achieve-

ments have taken human

civilization many steps forward.

Louis Pasteur, the French

chemist and scientist, could be

reckoned one such genius. His

contributions in chemistry,

microbiology and immunology

made him a legend in the

history of conquest of medical

science.

Louis Pasteur propagated and

successfully proved that germs

are the cause of fermentation

as well as many diseases. He

discovered that these germs or

living micro-organisms get killed

when exposed to very high

temperature. Pasteur's germ

theory and process of killing

germs by heating heralded a

new era and benefited the

common man immensely as it

saved much money and many

lives. It is for this reason that

he has become a house-hold

name. Pasteur received honours

in bounties in his lifetime as he

invented vaccines for one

animal disease after another;

but it is for his wondrous cure

of rabies, the killer disease,

that he will remain immortal in

the minds of men.

Louis Pasteur was born on

December 27, 1822, in Dole,

France. His parents moved to

the neighbouring town of

Arbois in 1827, where he got

105

his early education. Throughout

his life, his frail health was a

matter of constant concern, but

this could never deter him from

carrying out impressive series

of investigations which began

around 1847. During this time,

Louis Pasteur busied himself

with studies into the relation

between optical activity, crystal-

line structure and chemical

composition in organic

compounds.

His researches and experi-

ences always opened the way

for a new approach to the

study in the respective spheres,

Louis Pasteur

as they were characterized by

extraordinary experimental

skills, clarity of thought and

tenacity of purpose. All through

his life, he was obsessed with

science and its applications.

The problems of the day

always drew his attention. From

1857, he moved to the topic

of the process of fermentation

and started intensive studies

and researches in this field.

Ferments

During this time, the brewing

industry of France was facing

problems regarding the manu-

facture and preservation of

wine, beer and vinegar. After

thorough studies and elaborate

experiments, Pasteur concluded

that the process of fermenta-

tion which is the basis for

manufacturing wine, beer and

vinegar, involves the activities

of some specific living micro-

organisms. In Pasteur's time,

the popular belief was that

'spontaneous generation', a

chemical process, was the

cause of fermentation. But

Pasteur declared and proved

that it is the activity or multi-

plication of some specific living

micro-organisms that lead to

fermentation. According to his

researches, ferments which help

make bread, wine, beer, sour

milk, ammoniacal ferments

(ferments in urine) are living

micro-organisms which arise

and multiply during the act of

fermentation. He discredited

the dominant chemical theory

of fermentation and established

the biological theory of

fermentation with these basic

conceptions—

(a) the substance in fermenting

medium serves as food for

causative micro-organisms;

(b) each kind of fermentation is

caused by a specific micro-

organism;

(c) a particular chemical feature

of the medium of fermentation

can help or hinder the growth

of any one micro-organism

in it;

(d) air might be the source of

the micro-organisms that

appear in fermentation.

Preservation

Like fermentation, Pasteur

insisted, putrefaction, which is

generally defined as decomposi-

tion of vegetable and animal

matter, can be attributed to the

growth and multiplication of

living micro-organisms. As a

107

consequence of death and

putrefaction, carbon, nitrogen

and oxygen become available

as nutrients to support the life

of other organisms. He said

that putrefaction is merely the

fermentation of substances

containing a relatively high pro-

portion of sulphur and the

release of this sulphur in gas-

eous form produces the stink

commonly associated with

putrefaction.

Pasteur declared that the

prime industrial products,

namely the wine and vinegar,

could be preserved for a long

time by heating it in closed

vessels at a fixed and high

temperature. It would protect

the wine at a minimum risk to

its colour and taste.

Pasteur declared that the

micro-organism responsible for

alterations or decomposition in

wine, vinegar and beer could

be killed at high temperature.

This process of preserving wine

came to be known as

'Pasteurization' and at once

became popular at home and

abroad. Pasteur was awarded

many prizes by Exposition

Universelle in 1867 and by

agricultural and industrial

societies. Abroad, Pasteur's

name became inseparable from

the word 'Pasteurization' which

denoted heating of wine.

During the late 1860s the

pasteurization of wine and vin-

egar became almost common.

After Pasteur's discovery, it

became widely known that

germs which enter human body

through milk and water can be

killed at a high temperature. If

milk and water could be drunk

after boiling them, it would

prevent many diseases. Thus he

opened the way for pasteurized

milk which was to save millions

of children from the ravages of

tuberculosis.

In his studies on beer,

Pasteur sought to demonstrate

that the alterations or disease

of beer depend upon the

appearance and development of

foreign micro-organisms. He

described his process for

manufacturing beer which

emphasized the use of pure

yeast and carefully limited

quantities of pure air. Till this

day, his studies on wine, beer

108

and vinegar provide important

guidelines for the brewing

industry.

The discovery that living

micro-organisms are involved in

the process of fermentation led

Pasteur to conclude that living

micro-organisms are the cause

of many human and animal

diseases. In the late 1850s, in

spite of there being solid and

highly suggestive evidence that

germs might be the cause of

fermentation and diseases, the

germ theory did not find a

stronghold in medical concept.

It was during his intensive

studies into silkworm disease

around 1865 that Pasteur got

proof and became confident

that it is germs which are the

cause of many animal and

human diseases. Pasteur

devoted his last twenty years

almost exclusively to the germ

theory of diseases.

Silkworm studies

By 1865 French sericulturists

had become almost frantic

about a blight which afflicted

their silkworms—a disease that

proved disastrous to the

country's silk industry. Pasteur

began his studies on the silk-

worm disease and was struck

by the findings that there was

abundant presence of living

micro-organisms in the

intestinal canals of the infected

worms. Pasteur suggested

preventive measures against the

multiplication of living organ-

isms which, he concluded,

caused the silkworm affliction.

He recommended ways that

would increase the resistance of

the silkworms against any such

infection.

Anthrax menace

Following his succcess with

the silkworm problem by 1871,

he had a new, disease-oriented

laboratory to carry out his

experiments, along with an

annual research allowance of

6,000 francs. Pasteur now

turned to the menace of

anthrax. Anthrax was a fatal

epidemic disease of cattle and

sheep that posed a grave threat

109

to French agriculture and

animal husbandry. Pasteur

found out that the common

earthworm carried the bacteria

or microbes of anthrax from

infected, dead animals buried

under the surface of the earth

where healthy cattle grazed.

The cattle used to get infected

thus. As a preventive measure,

Pasteur suggested that animals

that had died of anthrax should

never be buried in fields meant

for grazing or growing fodder.

His study on anthrax and the

etiology of anthrax ushered in

a new epoch in the concepts

and thinking in the medical

domain. It flung open the

golden era of bacteriology. The

microbial theory of diseases

had now become established

and it was extended to tubercu-

losis, cholera, diptheria, typhoid,

gonorrhea, pneumonia, tetanus,

plague and many other common

human diseases. Pasteur and

the French school focussed on

the problems of immunity from

microbial diseases and devoted

time and energy on inventive

vaccines. The micro-organisms

of those diseases were studied

and isolated by Robert Koch,

the famous naturalist, and the

German school.

Cholera vaccine

In 1880 Pasteur proved the

microbial nature of fowl

cholera. It was a disease that

very often infected the poultry

and took a heavy toll, sparing

not a single chicken and caus-

ing grave concern. Pasteur

procured the fowl cholera

microbe in its most virulent

form. He cultured it at an

interval of two to three months

to find that attenuation had set

in. A prolonged exposure to

atmospheric oxygen led the

microbe to impotency. The

chickens were inoculated with

these cultured microbes. When

after some time they were

again inoculated with a second

virulent culture, the chickens

remained immune. Thus

Pasteur discovered fowl cholera

vaccine.

Shortly after his discovery of

fowl cholera vaccine, the city

of Paris presented him with the

110

ownership of some unoccupied

land near his laboratory. Here

he made well-planned arrange-

ments for the care and shelter

of many animals used in his

experiments.

The annual budget for

Pasteur's laboratory, fixed at

6,000 francs since 1871, was

supplemented by an annual

credit of 50,000 francs from

the Ministry of Agriculture of

France. Pasteur plunged heart

and soul into inventing an

anthrax vaccine. He cultivated

the anthrax microbe and

procured an attenuated culture

of anthrax microbe which

proved harmless to guinea-pigs,

rabbits and sheep. These three

species were susceptible to

anthrax. Pasteur wished to have

a large-scale trial. His announce-

ment of an effective anthrax

vaccine aroused great interest

all over.

On May 5, 1881, at Pouilly-

Le-Fort, Pasteur and his assist-

ants injected a herd of cattle

and sheep with the attenuated

anthrax virus. On May 17, each

of this group of cattle was

inoculated with a second

attenuated anthrax culture,

somewhat stronger than the

first. On May 31, Pasteur

injected a fully virulent anthrax

culture into each of these

inoculated animals. Pasteur

fixed June 2 as the date to

observe the results of this

vaccination. On the appointed

day, at Pouilly-Le-Fort, a large

crowd gathered to witness all

the vaccinated sheep and cattle

alive and healthy. The scene

rose to a dramatic climax as

the crowd congratulated Pasteur

and loudly applauded his work.

Pasteur's method of anthrax

vaccination spread throughout

Europe with striking success.

Sterilization

While emphasizing his views

on fermentation and putre-

faction, Louis Pasteur ventured

into medical topics, even before

1877. He made some remark-

able observations on surgery.

He suggested cotton-wool

dressings on wounds. This, he

said, would help trap the germs

and circulate pure beneficial

111

oxygen on the wounds and

thus prevent infection. He

advised surgeons as early as

1874 to sterilize their instru-

ments in boiling water or on

the flame before applying them

to the human body. He also

advised them to use sterilized

linen, bandages, and other

items during operations. He

laid the foundation for germ-

free surgery at a time when

post-operative infection and

consequent death was very

common. Joseph Lister, an

English surgeon, hearing of

Pasteur's proof of micro-organic

cause of putrefaction, began to

use carbolic acid to destroy

germs on the site of open

wounds. These antiseptic

measures prevented any post-

operative infection in Lister's

ward.

In 1878, during a lecture,

Pasteur claimed that a micro-

organism, 'vibrion septique', is

responsible for making the

blood putrid or septic. More,

this micro-organism easily

escaped detention. Pasteur said

that septicaemia might properly

be called 'putrefaction on the

living'. As a preventive measure

against septicaemia he again

advised surgeons to protect

patients' exposure to germs or

microbes scattered over all

objects, particularly in hospitals,

by using sterilized instruments,

lint, bandages, sponges and

linen.

Cure for rabies

All through his life, studies

on fermentation and success in

preventing many ariimal dis-

eases brought Pasteur world-wide

fame but with the discovery of

the rabies vaccine he rose to

the stature of a saviour.

In those days, people bitten

by rabid dogs had no chance

of survival from this dreaded

disease. Pasteur put all his

efforts and talent in search of

a rabies vaccine.

In May 1884, Pasteur

elaborated on the methods by

which the rabies virus had been

prepared in varying degrees of

virulence. Pasteur noticed by

experiment that prolonged

exposure to atmospheric

oxygen killed the virulence of

microbes of fowl cholera,

anthrax, horse typhoid and

saliva. He discovered another

method of attenuating microbes.

He found out that the microbes

in horse typhoid became

progressively less virulent to

guinea-pigs by successive

passages through rabbits. Saliva

microbes became increasingly

less virulent to rabbits by

successive passages through

guinea-pigs. Pasteur was soon

to exploit this new method of

attenuation against swine

erysipelas and rabies.

In Pasteur's time, swine

erysipelas, well-known as hog

cholera, was very prevalent and

113

Pasteur's concern for rabies, has been traced to a traumatic childhood experience in Arbois. In 1831, a mad wolf severely injured many people by violent bites, terrorizing the entire region of Arbois. Those who had been bitten by the wolf later succumbed. The horrible incident left a scar on his tender mind.

caused widespread havoc.

Pasteur cultured this microbe

to a point of harmlessness.

Inoculation of these cultured

microbes protected the hogs

from the effects of somewhat

less harmless cultures. He

injected the hogs with a series

of progressively more virulent

cultures and rendered the hogs

immune to the natural disease.

This method of vaccination

was used on more than

1,00,000 hogs in France

between 1886 and 1892 and

on more than a million hogs in

Hungary from 1889 to 1894.

To weaken the rabies virus,

Pasteur experimented by

passing it from dog to monkey

and then successively from

monkey to monkey. Its

virulence became totally

ineffective. On the other hand,

through successive passage

from guinea-pigs to rabbits, the

virulence of the rabies virus

rose to the maximum. By these

means, Pasteur noted, one can

prepare and keep on hand a

series of viruses of various

strengths, the most attenuated

of which are'harmless from the

outset but protect the inoculated

animal from the effects of

somewhat more virulent viruses.

These viruses in their turn, act

as a vaccine against still more

virulent virus, until eventually

the animal is always safe

against even the most virulent

and ordinarily fatal virus.

Putting his life at risk, Pasteur

used to suck saliva through a

glass tube from the foaming

mouths of rabid dogs, to inject

the material into rabbits. When

the disease began to rage in

the rabbits, he extracted strips

of their spinal cord, the chief

target of the rabies virus. He

suspended them in flasks in

which the atmosphere was kept

dry by addition of caustic

potash. He found that the

virulence in these gradually

diminished and ultimately

disappeared.

Using a spinal strip that had

been drying for about two

weeks, the first step in the

actual treatment was to mash a

portion of it in a sterile broth

and then to inject the resulting

paste into the animal to be

protected.

114

On successive days, the

injection came from progressively

fresher marrows and eventually

from a highly virulent strip that

had been drying for a day or

two. By this method, Pasteur

reported that he had rendered

fifty dogs of all types and ages

immune to rabies.

At this time, a nine-year-old

boy called Joseph Meister with

deep wounds from violent dog

bites approached Pasteur for

treatment. Pasteur suddenly got

an opportunity to test his

vaccine on human beings. One

can easily imagine his anxious

concern when he shot the first

injection into the young boy,

made from a fourteen-day dried

rabbit cord. The next day the

little boy got a stronger dose,

from a thirteen-day cord. The

treatment went on. Finally the

boy got a dose from the spinal

cord of a rabbit that had died

only the day before. As Pasteur

had hoped, the bodily resistance

had built up to a point where

even that ordinarily deadly

injection remained powerless.

The boy was safe.

The news spread like wildfire.

Scores of people bitten by dogs

came to Paris with the hope of

getting treatment. By the end

of 1886, about a year after the

first treatment of rabies, nearly

2,500 people had been treated

in Paris alone.

Idolizing Pasteur, people

bedecked him with lavish

praises, and the Government of

France recognized his contribu-

tion by showering him with

prizes. The most moving tribute

to Pasteur was the jubilee

celebration in 1892 in the

grand Amphitheatre of

Sorbonne where Pasteur was

honoured.

Pasteur Institute

Pasteur's most cherished wish

was fulfilled when, in 1881, he

was elected to the Academie

Francaise.

The greatest of all recogni-

tions was the establishment of

'Institut Pasteur' in Paris the

same year. People from all over

the world came forward to

donate for the Institute.

The Pasteur Institute today is

115

big and busy, bustling with

activity. Louis Pasteur was the

first director of the Institute. Its

aim was to fulfil Pasteur's idea

that it would come to the aid

of the sick and attack sickness

everywhere. The Pasteur

Institute came up with trained

researchers and started manu-

facturing serums and vaccines.

The Institute has a series of

triumphant achievements to its

credit. The diphtheria vaccine

was discovered in 1894 by

Dr. Roux who was Pasteur's

disciple. Given to children

today, it protects them from

this dreaded disease that had a

high mortality rate.

Over the years, the Pasteur

Institute has earned a reputa-

tion as the world's most

productive medical research

laboratory. One of its top

achievements is the B.C.G.

(Bacillus Calmette-Guerin, named

after two research workers,

A.L.C. Calmette and Camille

Guerin) vaccine. The B.C.G.

vaccine is given to every

newborn baby to prevent tuber-

culosis. Pasteur's research

workers also produced the first

antihistamine and the first

synthetic curare—a muscle

relaxant that stills muscle con-

tortion and makes organs lie

quiet, thus simplifying

abdominal surgery.

On the eve of the second

world war, Dr. Paul Giroud of

the Pasteur Institute, discovered

the typhus vaccine that saved

millions of people living in

poor sanitary conditions.

A specialist at the Pasteur

Institute, Dr. Pierre Lepine,

discovered the polio vaccine

along with two American

researchers working separately

in the United States. The polio

vaccine gives millions of

children protection from polio

every year. Before this, polio

used to infect children and

paralyse their muscles and

nerves, making them disabled

forever.

The contribution of the

doctors and researchers of the

Pasteur Institute in the medical

field is immeasurable. The

Institute has a chain of laborat-

ories and field stations all over

the world.

On October 5, 1895, Louis

116

Pasteur breathed his last. He

was honoured with a state

funeral and full military

honours. His body is kept in

the resplendent burial crypt of

the Pasteur Institute. Many

places and streets in France

have been named after Pasteur.

Pasteur is dead, but his

beloved Institute works on

tirelessly to save mankind from

the scourge of diseases.

Pasteur Institute

During the second world war, at the advance of German soldiers towards Paris, Joseph Meister, whom Pasteur first successfully treated for rabies, and who served many years as a concierge at the Pasteur Institute, committed suicide fearing he would have to open the Institute to the enemies and thus bring disgrace to the nation and to the great soul of Louis Pasteur!

10 LASER

Is there any light more

powerful than sunlight?

Yes, there is. Laser, which is

an abbreviation of Light Ampli-

fication by Stimulated Emission

of Radiation.

How different is laser from

sunlight? Sunlight is incoherent

in character; it fans out in

many directions and thus loses

intensity in the process.

In contrast, laser is coherent;

it flows in one direction. It does

not waver.

This makes laser mono-

chromatic. It means that laser

shows only one colour. This is

because every beam of laser

light has the same wavelength.

We know that light moves in

waves. When this occurs with

uniform ups and downs, light

emits a single colour. It

becomes monochromatic.

Sunlight is not mono-

chromatic. The rays of the sun

contain the basic colours. When

a beam of sunlight passes

through a prism, it splits into

seven colours—violet, indigo,

blue, green, yellow, orange and

red (VIBGYOR). Each colour of

light has a different wavelength.

The light, therefore, is not

concentrated.

There was light...

It started off as a spark of an

idea. A vague one, at that.

118

A Torch

A. Incoherent light B. Coherent light

H.G. Wells, the well-known

novelist, explored the idea first

in his novel, The War of the

Worlds.

The theme of the novel is

exciting. Martians attack the

earth. They are armed with

powerful, deadly weapons.

These weapons use powerful

beams of light which cut

through everything...walls, dams,

steel helmets and barricades.

The light destroys anything that

stands in its way. Large armies

are decimated in no time.

Houses collapse and for a

while, the Martians have the

upper hand. However, despite

powerful lights, Martians fall

prey to bacterial infection.

Buck Rogers as hero in the

cartoon series, uses a ray gun

which derives its strength from

the concept of laser.

These fictional reports aroused

interest among scientists. Many

scientists wondered whether the

idea could not be made into

reality. Why should such a

wonderful idea remain purely

fiction? They began to examine

the idea in depth.

Albert Einstein laid down the

means by which a powerful

light could be produced in the

laboratory. According to his

logic, every element is com-

posed of atoms. The atom is a

storehouse of energy. The

energy that the atom holds

depends on the electrons in the

atom. The atom exists, both at

119

B Laser

Scientists conceived the idea of the laser during the late 1950s and started developing the device in the early 1960s. Before Charles Townes worked on the theory that led to the making of the laser he developed maser—Microwave Amplification by Stimulated Emission of Radiation. Lasers amplify light, masers amplify microwaves—the electromagnetic waves used in radio, television and radar.

low and high temperatures.

When an atom absorbs heat,

its energy level goes up.

The atom, when it sheds

heat, releases energy. This

takes the form of heat or light.

But this light is not coherent. It

is not monochromatic. It has

beams of different wavelengths.

Einstein was of the opinion

that if a means could be found

of making this light mono-

chromatic, it would be very

powerful. He did not follow up

this idea. However, work on his

idea of producing a powerful

light began in the 1950s (See

box above).

Microwaves

Charles Hard Townes, a

research scholar at Columbia

University, New York, studied

the link between radiation and

120

atom. He needed microwaves,

waves of very short wavelength,

to continue the study. But

there was no known method of

producing these waves.

Townes decided to put

together the necessary equip-

ment. With some effort, he

made a machine which gave

him waves of very short wave-

lengths. Townes used the

microwaves to stimulate the

release of radiation. This is

known as emission. Townes

achieved this in 1951. At last,

scientists knew how to produce

microwaves. But there still

remained a problem.

Nobody knew how to

produce light of very short

wavelength. Townes, along with

A. Schawlow, carried out

extensive research in this field.

In 1958, they published their

conclusions. Their theory

indicated how light with very

short wavelength could be

produced and how it could be

made monochromatic.

According to their theory

when a beam of light of pre-

defined wavelength collides with

an atom, the atom reacts by

releasing a beam of light of an

equal wavelength. The two

beams of light with equal

wavelengths bounce on other

atoms. Thus the beams

multiply. Soon, there is a flood

of beams of light of identical

wavelength. They move in the

same direction. They hold

immense power.

Townes was awarded the

Nobel Prize for Physics in

1964, for laying the theoretical

base for laser.

Excited atom

However, the credit for

producing the first laser goes to

Theodore H. Maiman, an

American physicist.

He set out to produce the

necessary mechanism to produce

monochromatic light of short

wavelengths, and succeeded.

He took a synthetic ruby rod

and on either end he fixed

mirrors—one fully reflective and

the other partially so. The

choice of the mirrors was

deliberate. The fully reflective

mirror reflected the light which

fell on it, totally. When the

light, after reflection, reached

the partially reflective mirror,

some beams of light escaped.

1. Ruby rod 2. Lighted flash tube 3. Totally reflecting mirrors 4. Partially reflecting mirror 5. Excited atoms in a ruby rod 6. Laser light

1. Electron jumps to higher level 2. Incoming light excites the atom 3. Electron falls back to original level 4. Low energy level 5. High energy level

The light, which came from

a flash bulb through the ruby,

excited some of the ruby's

atoms. An atom became

excited when the absorbed light

energy changed the orbit of one

of its electrons. The excited

atoms released a ray of light as

their electrons dropped back to

low-energy orbits. This light

bounced onto another atom. It

drew out another beam of light

of the same wavelength. Soon,

there were hordes of light

beams. They were reflected on

the fully reflective mirror. They

bounced back and hit the

partially reflective mirror. Some

beams escaped and emerged as

laser. The light was mono-

chromatic. Every beam had the

same wavelength. The light was

very powerful and intense. It

did not waver. It did not stray.

Maiman made his discovery

public. The theory, set down by

Einstein and Townes, had

become a practical tool.

Versatile use

Could other mediums be used

to produce laser? The quest

began almost immediately.

One of the scientists who

joined this research was Kumar

Patel. He was working in the

122

United States of America. In

1964, he decided to try carbon

dioxide as a medium. He had

noticed that carbon atoms in

the gas released energy con-

tinuously. This held out hope.

The laser he produced was

incomparably powerful. There

had never been light with such

power. Patel argued that gas is

better than solid state crystals

as a medium for producing

lasers. This was a major

breakthrough.

Maiman and Patel had shown

the way. Soon, many other

scientists entered the field.

Each one tried a different

medium. Thanks to their work,

we have an infinite variety of

lasers. Each type has its use.

Lasers are used in many

fields—in industry, business

operations, surgery, beauty

care, agriculture, quality control,

road-laying, defence and com-

municatom. There is hardly any

field where lasers, of defined

strength, are not used.

Let us see how laser serves a

supermarket. The customer picks

up the articles he wants and

walks over to the cash counter.

The clerk at the counter holds

each article, one by one, over

a slit through which a laser

beam shoots out. The beam

reads the bar code on the

product and registers the price

in the computer. The computer

adds up the cost of the different

items and flashes the total

amount of the bill.

See how simple the

procedure is, how quick and

accurate! More and more

departmental stores the world

over are using lasers.

Clinical fields

Low-powered carbon dioxide

laser is of great help to

surgeons. Unlike other surgical

instruments, laser cuts and

cauterizes at the same time.

This is a big advantage. Laser

is used for delicate surgery.

The disorders of the blood

vessels which affect the retina

can be cured by the use of

laser beams, produced by a

medium of argon gas. Several

beams, at times as many as

2,000, rush into the mesh of

123

blood vessels in the retina.

These beams eliminate the

diseased vessels and repair

vessels which have ruptured.

Laser thus clears up the net-

work of blood vessels, restoring

normal sight to the patient.

Laser is used to cure yet

another common eye ailment—

glaucoma, a disorder in which

increased pressure within the

eye impairs the vision and

gradually causes total loss of

vision. This treatment takes

barely twenty minutes. It is

quick, easy, effective, and

painless.

Laser is used to treat cataract,

an ailment of the eye which

affects the aged. A thin film

The heating action of a laser beam is used by the surgeons to remove diseased body tissue. The beam burns away the unhealthy tissue in seconds without causing much damage to the healthy area.

Sgg^&jnr

Laser in surgery

forms over the lens of the

eyes, impairing vision. Till

recently, this used to be

removed by normal surgery.

Now, using laser beams the

film is melted away. The

patient gets quick relief. The

doctor implants an artificial lens

to provide vision. This may

eliminate the use of spectacles.

In many cases, after the

implant of the lens, a hazy

membrane forms in the eye.

This is a form of secondary

cataract, again requiring treat-

ment using laser.

Dr. Herald Horn, an opthal-

mologist, developed a laser

which uses the element erbium

as a medium. It produces high

frequency laser beams which

penetrate the cornea and gently

wipe off the thin membrane in

a trice. The patient recovers

within 24 hours.

Lithotripter

It is not merely in treatment

of disorders of the eye that

laser plays a role.

Take, for instance, modern

treatment for kidney stones.

The lithotripter is the standard

equipment used for treatment,

which eliminates use of surgical

knife. The lithotripter sends out

high frequency sound waves.

These sound waves break the

stones into bits which pass out

easily through the urinary tract.

The lithotripter can be used

only to get rid of stones lodged

in the kidney or the upper part

of the uninary tract. Stones

lodged in the lower part escape

the sound waves, being warded

off by the pelvic bones. Here

too laser offers a solution.

The laser beam is flashed

through a fibre tube inserted

into the ureter. The laser chips

away the stone, without harm-

ing the surrounding tissues.

Once the stone has been

reduced to manageable bits, the

residue is scooped out.

The method was tested by

urologists, Stephen P. Dretler

and John A. Parrish, in the

United States of America, on a

batch of 34 patients to begin

with. The method was successful

in all but one case. The

urologists felt that the lithotripter

125

and the laser beam, together,

can bring relief to most patients.

Surgical intervention to cure

stones in the kidney may

become obsolete in this case.

A powerful tool

The major advantage of a

laser beam has been recognized

by surgeons all over the

world—it 'cuts cleanly and

sterilizes at the same time'.

Dr. Janos Voros, of the Laser

Research Foundation of New

Orleans, adds, "If the laser is

used properly, it is safer than

other instruments."

The areas where laser beams

can bring relief to patients are

unlimited. Laser destroys

ovarian cysts. It removes tubal

pregnancy which often

threatens the life of the mother.

It is used to destroy some

forms of brain and spinal

tumours. Dr. Leonard Cerullo,

of Northwestern University

Medical School says, "Lasers

have made inoperable tumours

operable and high-risk tumours

less high-risk... The laser

gives a good surgeon a big

advantage."

Medical research is turning to

lasers to find new applications.

Garrett Lee of the University of

California used laser beams to

destroy fatty deposits of

cholesterol that block arteries.

The laser beam is also used in

major surgeries of the heart.

Some Russian beauticians

developed the laser to help

restore a youthful look to the

face. The technique they use is

simple. Low-powered laser

beams pick up the sags and

the bags on the face. The

beams even out the wrinkles

and furrows. So the face looks

smoother, brighter, younger.

This sort of beauty aid is

now available in Europe, the

United States of America and

in some major Indian cities, too.

What does one do with a

tattoo that no longer appeals?

Till recently, there was no easy

way out. The tattoo stayed for

life. But now heat from a

2-watt argon laser cauterizes

the blood vessels on the surface

of the skin. When the laser

beam runs over the tattoo, it

126

gently scrapes the mark off.

The tattoo vanishes in a trice.

Some farmers in France, who

have vineyards, have sought

order in their plantations

through the laser. They know

that the laser beams move in

perfect, straight lines without

wavering. The farmers also

know that well-aligned rows of

grapevines give maximum

production. Further, it is easier

to prune, trim, weed out pests

and unwanted growth, and

harvest the crop if the creepers

are properly aligned.

Oliver Brun, a research

engineer, working for a leading

champagne producer in France,

turned to the laser. The laser

beam acts as a guide. The

tractor which lays the seeds is

guided along a straight line by

the laser beam. It keeps

straight, even when the land is

steeply graded.

The saplings, when they

sprout, are evenly spaced. They

get enough light. They have

sufficient room to draw susten-

ance from the soil. There is no

need for replanting the saplings

if the seeds are laid with the

help of laser. This brings about

much reduction in the cost of

managing the vineyard. Further,

because every plant gets the

chance of enough nourishment,

light and water, the production

of grapes increases. The farmers

get more profits.

Compact disc

Does laser have a role to

play in providing good music?

In 1898, Emile Berliner, a

German-American inventor,

produced the first gramophone

record. You must have seen

gramophone records. The

sound tracks are etched on the

plate. When the record rotates,

a needle glides through the

grooves. The vibration touches

the sound chord and music is

produced.

Gramophone records have

become almost obsolete now.

In 1983, a new record called

the Compact Disc was made. A

laser beam scans small depres-

sions on a metallic disc. It

transforms the light impulses

into electrical impulses and the

127

music can be heard. The disc is

only 25 cms. in diameter and it

is easier to store. There is no

wear and tear. The quality of

reproduction remains unaffected,

even after hundreds of runs.

Scratches and fingerprints too,

do not affect the record. For,

the disc is wrapped in a

protective film. Thus the

Compact Disc retains its quality,

forever.

That brings us to the role of

the laser in maintaining quality.

Dr. Philip Wyatt, a physicist,

working with an American

concern, has developed a

technique to use laser to test

the quality of wine. He

specialized in bio-medical

instruments. He noticed that

the quality of the wine

depended on the size of the

protein particles present in it.

The smaller the size of the

particles, the better the taste.

This provided him the base

for making an instrument to

test wine.

The instrument projects a

laser beam on to a test-tube

containing a sample of the

wine. The intensity of the light,

scattered by the particles, is

measured. The direction in

which the light gets scattered is

also measured. Each wine

responds differently to the laser

beam. The intensity and the

direction of reflection vary.

These are noted on a graph

for each sample. The best wine

provides curves which do not

have high peaks and dips. The

swerve from the median is

limited. The flatter the curve,

the better the wine is. A study

of the curve indicates the

quality of the spirit.

In communication

Sound is a means of

communication.

In 1880, Alexander Graham

Bell invented the photophone.

He used a mirror-and-lens

system to transmit his voice to

a sunbeam. He was thrilled by

the success of his experiment.

He said, "I have heard a ray of

sun laugh and cough and sing."

Today, instead of sunbeams,

scientists use laser beams for

communication. Since lasers

produce light waves of extra-

128

ordinarily high frequencies, an

enormous quantity of informa-

tion gets transmitted much

faster than through normal

means with which we have

been familiar.

In 1983, Won Tien-Tsang of

Bell Laboratories tried an

experiment which demonstrated

the speed and accuracy with

which laser beams can carry

out information. He developed

laser microchips. These chips

are no larger than grains of

salt. They produce light pulses,

which are carried by glass fibres.

Glass fibres are more efficient

than normal conduits like

copper or aluminium used in

electrical wires. Glass fibres

keep out external interference,

so there is very little distortion

of the text that goes through

them. The quality of trans-

mission too is good. The

message moves fast through

the laser carried by- glass fibres.

It was stated that the entire

contents of a 30-volume

encyclopaedia transmitted

through the new device took less

than a second!

Thanks to glass fibres or

fibre optics, computers have

become slimmer and more

handy. Here too, laser plays a

major role.

Robots shall be powered by

laser. They shall perform many

specially programmed delicate

tasks, with ease and perfection.

Some years back, U.S.A was

apprehensive of a war with the

Soviet Union, now Common-

wealth of Independent States

(CIS). The Americans were

worried about missiles, laden

with explosive atomic packs,

rushing across space, targetting

major industrial and defence

installations.

Ronald Reagan, the then

President of U.S.A., funded a

programme named Star War. It

was also known as SDI, the

Strategic Defence Initiative.

Laser beams were to be used

in the plan. According to the

scheme, 24 satellites would be

put in space. The satellites

would go round the earth, in

orbits about 1,300 to 1,600 km.

above the earth. At any given

time, eight of these satellites

would keep the Soviet Union

under close scrutiny. The

129

satellites would identify any

missile launched from submar-

ines. On detecting a missile,

the satellite would adopt

measures to intercept the

missile. The satellite would use

mirrors to send out powerful,

chemically-activated laser

beams. These beams would

destroy the missile, even as it

moved towards its target.

Lasers guide bombs precisely

to the target. It tells if there is

an obstacle. The laser beam

pin-points the object and

indicates the direction in which

the cannon should be turned

for a direct hit.

Howard H. Boehmer, a

former Vice-President of

Hughes Aircraft Company, said,

"You couldn't shoot accurately

beyond 1,000 to 1,500 m.

With modern laser, targets are

vulnerable up to 3,000 m."

The fields in which the laser

can assist man are infinite,

holding innumerable possibilities.

11 NANO-TECH

What drives the modern

civilization? Electric motors,

electric dynamos, electric

batteries, and so on. Now

imagine all these work-horses

in very minute sizes—as small

as a mosquito or even smaller.

All modern gadgets, equipment,

instruments, in fact, everything

that is composed of these

work-horses will become

smaller, more compact and yet

more effective than what they

are today. Thanks to the

wonder wand of nano-

technology! The world will then

become more easy to manage,

more energy-efficient and more

environmentally sound. No

more will technology look

threatening and beyond control.

'Dwarf'

What is nano-technology?

'Nano' means 'billionth of a

metre'. One metre is 100 cms.;

a foot-ruler is about 30 cms.

One billionth of a metre is one

metre divided by one billion

(1000,000,000), that is,

0.0000001 cm. Imagine

something as small as that.

Look around! What can be as

small as that? A cockroach? No!

An insect! No! The pointed tip

of a needle? No! Then, what?

131

The billionth of a metre is just

three atoms kept side by side!

And an atom yet is the

smallest unit of matter!

In Greek, 'nano' means

'dwarf. Dwarfs are short, little

beings that appear in fairy and

witch tales. Nano-technology,

therefore, stands for 'dwarfish'

technology. It is a dwarf even

when compared to the most

modern and advanced mini-

and micro-technologies that are

needed to build very small and

sophisticated computers! For

instance, even nano-robots

which can enter a human body

and perform any operation are

now possible to build! Also,

biologically important molecules

(two or more than two atoms)

of use in industries and medicine

are likely to be created using

nano-technology.

Engineers in the United States of America are developing motors which are so tiny that they can pass through the eye of a needle. The size of the motor is only about two-thirds the width of a human hair. Some 10,000 of them couid fit into a pea!

v . , I,., t J

Inspiration

What could have inspired

scientists to think of minute,

nano-sized things? Simple!

Nature! It needed the genius of

that charismatic physicist,

Richard Feynman to consider

micro-organisms and minute

living beings as very minute

machines. The machines are

built up of molecules and

packed with information on

how to function! For instance,

if a mosquito has to fly, some

information is exchanged bet-

ween its brain and wings that

enables it to fly.

On December 29, 1959,

Feynman delivered the lecture:

'There's plenty of room at the

bottom' to the members of the

American Physical Society. In

the lecture he talked about the

molecule-sized machines and

how they could be built using

the knowledge of science then

available. In fact, he gave a lot

of playful and fantastic

suggestions on how the then

available knowledge of science

could be used to build those

machines. But those were the

132

Engineers in the United States of America are developing motors which are so tiny that they can pass through the eye of a needle. The size of the motor is only about two-thirds the width of a human hair. Some 10,000 of them could fit into a pea!

days when even an ordinary

computer by present standards

occupied a huge hall! Most of

the scientists in the audience

listened to Feynman's ideas

with amusement. Some even

thought that Feynman had

gone crazy!

Surely, no! Feynman had a

vision which nobody in the

audience had. To conceive of

minute organisms as informa-

tion-packed machines was not a

joke even in the '50s, although

most, if not all, of the inven-

tions by man are nothing but

copies of things available in

nature whether it is a fan or an

aeroplane.

However, Feynman's lecture

remained a vision of a genius

and was forgotten by most of

the scientists in the audience

until in 1986, K. Eric Drexler,

a Stanford University engineer,

made the subject very attractive

for the public. He wrote a

book, Engines of Creation,

which caught the imagination

of the people. In the book he

not only talked about the

possibility of building minute

molecule-sized machines but

K. Eric Drexler

also coined the term 'nano-

technology'. He referred to the

technology of controlling atoms

(or molecules) at the scale of

nanometer as 'nano-technology'.

Engines of Creation intro-

duced the people to a new

outlook altogether. It made

nano-technology the most

curious thing all over the world.

In 1981, two scientists,

Heinrich Rohrer and Gerd

Binning at IBM Zurich

Research Laboratory, prepared

the ground for this novel

technology. They built the first

Scanning Tunnelling Microscope

(STM). The microscope is so

powerful that it can detect

individual atoms! It can, there-

fore, be used to build nano-

things atom by atom! It is not

133

much different from erecting a

building brick by brick!

Fabrication

When you sees a mosquito,

you may not marvel at its

construction because you tend

to think it is a creation of

nature which had evolved over

several millions of years. You

will certainly wonder how a

mosquito-sized or even smaller

electric motor with moving

parts can be fabricated.

Surprisingly, there are not

one but two methods of

fabrication. One method is

somewhat like carving out a

bridge from a large block of

steel, just as one carves a

beautiful sculpture out of a

stone. It is known as

'photolithography' or 'micro-

lithography' and is nowadays

commonly used to carve out

minute electrical circuits on a

silicon chip—the brain of a

computer. The other method is

recent and is like building a

bridge out of bricks and steel.

A Scanning Tunnelling

Microscope is the tool.

Photolithography is not much

different from photography. In

fact, it is photography in three

dimensions. Suppose a three-

storey house has to be built,

with a different design for each

floor. By using photolitho-

graphy, each floor of the house

is first designed and then built

separately. All the floors are

thereafter fixed one above the

other in the order in which it

is required. Similarly, a nano-

structure, whether a wheel or

an electrical circuit, is divided

into thin layers. Each layer is

separately designed, carved out,

and then all the layers are

assembled to form the complete

structure!

What about the fabrication of

a single layer of a nano-thing?

It is also surprisingly simple! To

draw letters or pictures, one

often takes the help of a

stencil. Similarly, a stencil of

the desired design of the single

layer of a nano-thing is made

using a computer. Just as

sunlight or for that matter any

light source is needed to copy

a drawing from an ordinary

134

stencil, the finely-designed

stencil of a nano-thing also

needs light but of a special

type. It is special in the sense

that it is a light which is not

seen by human eyes. In the

seven colours of the spectrum,

it is beyond the violet end. It

is, therefore, called 'Ultraviolet'

Ultraviolet light is passed

through the stencil to fall upon

a blank. The blank, made of

silicon or gallium arsenide, is

coated with a polymer material

that resists light. The material

degrades on exposure to the

light falling through the stencil

and so leaves markings on the

blank. In other words, the

design of the stencil is

transferred to the blank. Using

chemicals all the rough edges

are washed away.

The silicon or gallium

arsenide blank with clear-cut

design is made ready for

further work, just as a letter or

figure drawn using an ordinary

stencil is ready for filling in

with colours. Three processes

are mainly used for modifying

the design. They are etching,

deposition and doping. During

etching, the design drawn is

further chiselled deep into the

blank by using a fine beam of

radiation. During deposition, a

layer of new material such as a

tough ceramic coating or a

metal like platinum is deposited

on the drawn design. During

doping, the exposed design on

the blank is bombarded or

bathed with electrically charged

particles of some elements

to change their electrical

properties.

Powerful microscopes such as

the Scanning Electron Micro-

scope, the Atomic Force

Microscope and the Scanning

Tunnelling Microscope are used

to examine the handiwork

performed on the blank. A

large number of instruments

and equipment check whether

the design has acquired the

desired electrical properties or

not by passing minute currents

of electricity through its various

portions. If the handiwork is

not performing satisfactorily,

the processes are repeated for

the desired results.

Photolithography is able to

bring down the size of the

135

structures to 100 nanometres,

that is, 10 millionth of a metre.

To further reduce the size of

structures, one needs finer

tools, just as one needs a pin

with a finer point to produce a

smaller hole. Instead of ultra-

violet light, finer X-rays and

electrons are used so that

structures smaller than

20 nanometres could be built.

Various types of mechanical

devices with free moving parts

have been wholly built or built

in parts and then assembled. In

fact, a U.S. laboratory has

fabricated a compact manu-

facturing system which designs

and fabricates these tiny

structures.

Nano-structures

The Scanning Tunnelling

Microscope was originally

invented to examine and map

out individual atoms on any

surface. But when it was found

that the sensing 'eye' of the

microscope could as well pick

up an atom from any surface

and place it in an appropriate

position, it was used to build

nano-structures.

In 1990, the ability of the

microscope to pick and move

atoms was first demonstrated at

the IBM Center, California,

U.S.A. Thirty-five atoms of the

element Xenon were picked up

and placed on the surface of

the metal nickel to spell out

the company's logo 'IBM'—one

atom thick!

This demonstration created a

stir in the scientific community

as it became evident that the

powerful microscope can be

used as a machine tool for

handling atoms. Besides it can

also be used to create

nanometre-sized grooves on a

silicon blank for the fabrication

of nano-things.

136

The world's tiniest Toyota which is only 4.8 mm long has been manufactured by Japan's biggest car components company. It took over two months to build this microcar which is a replica of the Toyota Model AA. It has been decided that an environment-friendly miniaturized electric engine will be used to run it.

Sensitive sensors

The most remarkable nano-

device built to date is the mite-

sized Scanning Tunnelling

Microscope invented by Noel

MacDonald and his team at the

National Nanofabrication

Faculty at Cornell University,

and by Calvin Quote and his

team at Stanford University,

both in U.S.A.

The stylus or sensing point

of this powerful yet small

microscope has two tips instead

of one. These tips act as

'nerves' of the microscope.

Each tip weighs less than one

billionth of a gram, where one

gram is the weight of a plastic

spoon. One tip stands still and

the other vibrates. If a slight

disturbance such as noise, light

flash or a movement appears in

the surroundings, it sets the tip

vibrating making it a highly

sensitive sensor!

A California-based company

has already built a sensor which

determines the blood pressure

inside the heart during an

operation. Other pressure

sensors for use in the

carburettors of vehicles, heating

and air-conditioning systems are

also being built as there is a

demand for sensors in the

market.

Scientists foresee the use of

such sensors to sense and

monitor hundreds of pollutants

in air, water and on beaches.

In fact, sensors that would

open doors on 'smelling' the

scent of the owner of the

house, throw open windows of

a garage if the poisonous gas

carbon monoxide is detected in

the exhaust of a vehicle, and

so on, could be built.

Even sensors that could hear,

smell, taste and feel are likely

to be invented and manu-

factured in future years. Such

sensors would be fitted in

multi-purpose robots which are

likely to be built before long.

Science fictions in which robots

eat, drink and crack jokes do

not seem as unrealistic today as

they did when they were written!

First micro-devices

Isaac Asimov's classic science

fiction, Fantastic Voyage was

137

subsequently made into a major

film. In the novel, a huge

submarine is converted into a

minute particle and injected

into the body of a human

being whose ailment has to be

corrected. Today, the fabrication

of such a minute self-propelling

device is on the anvil! The

possibility of building a micro-

robot which would enter the

heart of a patient through an

artery, inspect the situation,

remove any clogging material

either physically or by aiming a

laser beam at it is not too

far away!

Already in 1987 the first

micro-device with moving parts

was fabricated in the U.S.A. It

has a tiny gear wheel which

can be spun by jets of air. It

set off scientists on the road to

build a variety of micro-devices

with moving parts such as

micro-pumps, micro-valves,

micro-turbines, and so on. A

micro-pump, for instance, could

be used to inject drugs into the

body of a patient. A 4.8 mm

Toyota car (as mentioned in

the box on page 136) could be

easily used, like the submarine

in Fantastic Voyage, to enter a

human body or a nuclear

reactor to examine arteries or

cooling tubes respectively and

conduct repair work!

Some nano-sized items have

already been built. For instance,

a minute fuel cell which could

supply electricity to the micro-

scopic components of a circuit,

has been built. A nano-wire for

the passage of minute electric

currents has also been built. All

these 'first generation nano-

devices' are likely to speed up

the race to manufacture smaller

and still smaller things. They

could also be used to mimic

some phenomenon occurring in

nature so that it could be

understood and utilized for the

benefit of mankind. For

instance, the inner working of

138

Scientists at IBM Zurich Research Laboratory in Switzerland have invented an ultraminiature abacus in which spherical carbon molecules sl iding along microscopic copper grooves act as the counting beads for performing arithmetic calculations.

a leaf could be mimicked to

understand how a plant

circulates water, carbon dioxide

and oxygen through its veins

and stomata.

The United States of America,

Germany and Japan are spear-

heading the field of nano-

technology. Meanwhile, K. Eric

Drexler and others have not

kept quiet. In his second book,

Unbounding the Future, Drexler

and his followers have described

a vision in which nano-

technologies would replace

most of the present day giant-

scale technologies required in

refining oil, manufacturing

paper, extracting oil from deep

wells and minerals from the

ground.

However, most nano-

technologists scoff at Drexler's

vision. They think that he is

stretching his ideas too far. For

him nano-technology has

almost become a religion.

Nano-technologies are certain

to come in in a big way but

that does not mean that the

present technologies would

become obsolete and would go

into disuse. For instance, nano-

t — — \

Thousands of pieces of mail are delivered every day at the Federal Bureau of Investigations (FBI) office in Balt imore, Maryland, by Marvin—a robot!

Ripley's Believe It or Not V 1 _ J technology would manufacture

only the critical components of

a gadget. The chip in a

computer would be manu-

factured by nano-technology but

the entire computer would be

manufactured by the present

technologies. Some scientists

also have doubts about whether

all types of nano-devices could

really be built because, while

positioning atoms for building a

nano-device any minute disturb-

ance due to heat currents,

radiations, would affect its

fabrication.

Ugly face

In the years to come, nano-

technology would appear in the

news, time and again, as its

products and discoveries leave

the doors of the laboratories.

However, a revolution would

139

Thousands of pieces of mail are delivered every day at the Federal Bureau of Investigations (FBI) office in Balt imore, Maryland, by Marvin—a robot!

Ripley's Believe It or Not

come where theoreticians,

fabricators, engineers,

physicists, chemists and

material scientists join hands to

manufacture products which

benefit the man on the street.

Before it is believed that nano-

technology would provide

products that would do good to

the society, it should not be

forgotten that any new

technology also brings perils.

For instance, the same nano-

robots which in hundreds and

thousands could clear the

surface of a submarine, the

choked pipe of a drain, and

enter a person's bloodstream to

clean any clogging material,

could also be employed for

socially dubious, harmful and

destructive purposes.

How such a wonderful

technology is likely to affect

our life style is difficult to

imagine at the moment.

The computer was originally

invented to speed up calcula-

tions but it is today being used

for various purposes from

making railway ticket reser-

vations to talking books.

Science itself could be shaken

by nano-technology. The vitally

important elementary particle,

electron, the backbone of

electronics and the electronics

industry, has been found to

behave in a bizarre manner in

the very minute nano-structures.

In fact, this very behaviour of

the electrons is likely to be

used to create novel technologies

for the 21st century!

140

Everything that happens in and around us is science.

Science lurks behind every known phenomenon, for instance, friction.

An active awareness would give us the 'scientific temper' and make us realize the importance of

science in human progress. The book brings together a few

concepts which we take as normal but hold scientific truths.

Its purpose is to encourage the young reader

to develop a live consciousness.

E 330

ISBN 81-7011-784-4