from atom to nano-tech.pdf
DESCRIPTION
Atom To Nano-TechTRANSCRIPT
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: [email protected] 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