Children's Science Encyclopedia E-Book

A.H. Hashmi

• Herausgeber: V&S Publishers
• Kategorie: Für Kinder und Jugendliche
• Sprache: Englisch
• Veröffentlichungsjahr: 2018

Seitenzahl: 511

Beschreibung

Familiarises children with important happenings in the scientific world

Leseprobe

Published by:

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© Copyright: ISBN 978-935-05723-0-6

DISCLAIMER

While every attempt has been made to provide accurate and timely information in this book, neither the author nor the publisher assumes any responsibility for errors, unintended omissions or commissions detected therein. The author and publisher make no representation or warranty with respect to the comprehensiveness or completeness of the contents provided.

All matters included have been simplified under professional guidance for general information only without any warranty for applicability on an individual. Any mention of an organization or a website in the book by way of citation or as a source of additional information doesn't imply the endorsement of the content either by the author or the publisher. It is possible that websites cited may have changed or removed between the time of editing and publishing the book.

Results from using the expert opinion in this book will be totally dependent on individual circumstances and factors beyond the control of the author and the publisher.

It makes sense to elicit advice from well informed sources before implementing the ideas given in the book. The reader assumes full responsibility for the consequences arising out from reading this book. For proper guidance, it is advisable to read the book under the watchful eyes of parents/guardian. The purchaser of this book assumes all responsibility for the use of given materials and information. The copyright of the entire content of this book rests with the author/publisher. Any infringement/ transmission of the cover design, text or illustrations, in any form, by any means, by any entity will invite legal action and be responsible for consequences thereon.

PREFACE

Children are inquisitive by nature. They are forever curious about the world around them and want to know more about it. Though they have textbooks for their reference, still they can never quench their thirst for knowledge completely. Encyclopedias are specifically designed to bridge this gap. They help to nurture the hidden Albert Einstein or Marie Curie in the children.,

Children’s Science Encyclopedia in 17 volumes is one such unparalleled effort in this direction. All the essential subject areas, from Universe and Environment, Plants and Animals, to Human Body, are covered in this comprehensive encyclopedia. Readable entries integrated with informative illustrations make the text lively and interesting, thus enabling better understanding of the topics covered.

Matchless in approach and presentation, Children’s Science Encyclopedia is certain to find appreciation in the eyes of students and also general readers, for being a one-stop comprehensive guide of the various aspects of Science. A must buy for school libraries and also individual households!

—Publishers

Contents

1. Universe

1. Space

2. Stars

3. Pulsars, Black Holes and Quasars

4. Galaxies

5. The Sun

6. The Solar System

7. Mercury

8. Venus

9. Earth

10. The Moon

11. Mars

12. Jupiter

13. Saturn

14. Uranus

15. Neptune

16. Pluto

17. Asteroids

18. Meteors and Meteorites

19. Comets

20. Exploring Space

21. Journey to the Moon

2. Earth

1. Origin of the earth

2. Earth and the atmosphere

3. Lithosphère or crust

4. Continents

5. Rock

6. Earthquakes

7. Mountain formation

8. Folds and faults

9. Volcanoes

10. Deserts

11. Geysers

12. Hot springs

13. Crater lakes

14. Erosion

15. Oceans

16. Rivers

17. Waterfalls

18. Underground water

19. Caves and caverns,

20. Weather and climate

21. Fog, Mist and Snowfall

22. Clouds

23. Rain

24. Cyclones

25. Glaciers

26. Arctic regions

27. Petroleum

3. Life on Earth

1. Geological Time

2. Fossils

3. Life in the Oceans

4. The Mesozoic Era

5. Dinosaurs

6. Flying Reptiles

7. Archaeopteryx—The First Bird

8. The Cenozoic Era

9. Plant Evolution

10. Early Mammals

11. Early Man

4. The Plant Kingdom

1. The Plant Kingdom

2. Algae

3. Fungi

4. Bacteria

5. Bryophyta

6. Ferns

7. Gymnosperms and Angiosperms

8. Ecological Classification of Plants

9. Useful Roots

10. Underground Stems

11. Photosynthesis

12. Defoliation

13. Structure and Functions of a Flower

14. Insectivorous Plants

15. Tallest Trees

16. Parasitic Plants

17. Types of Forests

18. Poisonous Plants

19. Uses of Plants

5. Animal Kingdom

1. Animal Kingdom

2. Protozoa and Metazoa

3. Molluscs

4. Insects

5. Crustaceans

6. Echinodermata

7. Pisces

8. Amphibians

9. Reptiles

10. Birds

11. Mammals

12. Nests

13. Migration of Birds

14. Speeds of Animals

15. Maximum Lifespans of Animals

6. The Human Body

1. Living Cells

2. The Human Skeleton

3. Muscles

4. The Blood System

5. Circulatory System

6. Heart

7. Skin

8. Brain

9. Digestive System

10. Excretory System

11. Respiratory System 12, Eye

13. Ears

14. Teeth

15. New Life

7. Environment & Pollution

1. Ecology

2. The Living Planet

3. Cycles of Carbon, Nitrogen, Oxygen and Hydrogen in Ecosystem

4. The Food Chain

5. Saving the Soil

6. Acid Rain

7. Pollution

8. Air Pollution

9. Ozone Depletion

10. Water Pollution

11. Noise Pollution

12. Losing Forest

13. New Species

14. Wildlife Under Threat

8.Transport

1. Invention of Wheel

2. Bicycle

3. Railways

4. Ships

5. Hovercraft 6, Motor Car

7. Motor Cycle

8. Aircraft

9. Jet Plane

10. Helicopter

11. Space Shuttle

9. Sound

1. What is Sound?

2. Mechanical Waves

3. Shock Waves

4. Noise

5. Reflection of Sound

6. Doppler’s Effect

7. Interference

8. Beats

9. Diffraction of Sound

10. Ultrasonic Waves

11. Bounded Medium

12. Vibrations of Air Columns

13. Stationary Waves

14. Characteristics of Sound

15. Resonance

10. Development of Chemistry

l.The Forefathers of Chemistry

2. Alchemy

3. Uses of Chemistry in Everyday Life

4. Branches of Chemistry

5. Invention of Gases

6. Medicines

7. Vitamins and Hormones

8. Elements

9. Organic Chemistry

10. Plastics

11. Chemical Fertilizers

12. The Atomic Theory of Matter

11. Energy

1. Energy

2. Solar Energy

3. Wind Generators

4. Hydroelectric

5. Powers, Geothermal Power

6. Coal

7. Mineral oil and Petroleum

8. Fuel Gases

9. Nuclear Energy

10. Nuclear Reactors

12. Force & Movement

1. Displacement, Distance, Speed & Velocity

2. Centripetal and Centrifugal Force

3. Newton’s Laws of Motion

4. Jet Propulsion

5. Centre of Gravity and Equilibrium

6. Universal Gravitation

7. Escape Velocity

8. Artificial Satellites

9. Rotation

10. Friction

11. Elasticity

12. Periodic Motion

13. Simple Machines

14. Systems of Un its

13. Communication

1. Communication

2. Printing

3. Photography

4. Radio

5. Radar

6. Cinematography

7. Reproduction of Sound

8. Telephone Network

9. Fax

10. Satellite Communications

11. Television

12. Video

13. Computer

14. Electricity & Megnetism

1. Electrostatics

2. Atmospheric Electricity

3. Electric Supply

4. Electric Shock

5. Sources of Electromotive Force

6. Dry Cell and Lead Accumulator

7. Electric Bulb and Electric Heater

8. Electrolysis

9. Simple Circuit

10. Electric Generator and Electric Motor

11. Transformer

12. Magnets and Magnetic Field

13. Ferro-Magnetic Substances

14. Electromagnet

15. The Earth’s Magnetism

15. Minerals & Metals

1. Minerals

2. Metals

3. Metallurgy

4. Gold

5. Silver

6. Iron

7. Copper

8. Manganese

9. Tin

10. Mercury

11. Aluminium

12. Lithium

13. Beryllium

14. Lead

15. Magnesium

16. Platinum

17. Uranium

16. Scientists and Inventions

1. Scientists and Inventions

2. Galileo Galilei (1564-1642)

3. Sir Isaac Newton (1642-1727)

4. Sir Humphry Davy (1778-1829)

5. Michael Faraday (1791-1867)

6. Charles Robert Darwin (1809-1882)

7. Friedrich Wohler (1800-1882)

8. Gregor Johann Mendel (1822-1884)

9. Louis Pasteur (1822-1895)

10. Friedrich August Kekule (1829-1896)

11. Thomas Alva Edison (1847-1931)

12. Albert Einstein (1879-1955)

13. Enrico Fermi (1901-1954)

14. J. Robert Oppenheimer (1904-1967)

15. Dr. Homi Jahangir Bhabha (1909-1966)

16. Great Inventions

17. Science and Technology

17. Light

l.Light

2. Spectrum

3. Solar Spectrum and Electromagnetic Spectrum

4. Fluorescense and Phosphorescence

5. Refraction of light

6. Mirage

7. Lenses

8. Reflection of light

9. Sight and eye

10. World of colours

11. Microscopes and telescopes

12. Laser

UNIVERSE

SPACE

Space is the vast region with no known boundaries beyond the Earth’s atmosphere. It is the empty area extending in all directions to infinity. The solar system, the stars, galactic dust and galaxies, regions between the galaxies, all form parts of space. Space has no atmosphere. It appears black during the day as well as at night. It does not inhabit any living organism.

Man has been trying to collect information about space with the help of powerful radio telescopes, rockets, satellites, space-crafts and space probes. These space explorations have revealed many mysteries and enhanced man’s knowledge about it.

STARS

Stars are huge spheres of glowing gases. They vary considerably in size, colour, temperature, brightness and distance from the Earth. The Sun is also a medium-sized star. It is comparatively nearer to the Earth, hence it looks bigger in size.

Stars appear to twinkle because they are seen through the Earth’s atmosphere. Stars also seem to move from east to west across the sky. This ‘movement’ is actually caused by the spinning of the Earth. Stars are often classified according to their size. The four major sizes are super giant, giant, medium and dwarf.

The colour of a star indicates its surface temperature. The hottest stars are blue. Red stars are somewhat cooler, having a temperature of about 2800°C. The Sun and other yellow stars have surface temperature of about 5500°C. Rigel, the blue-white giant star, has a diameter 80 times larger than that of the Sun and is 60,000 times brighter than it.

A spacecraft takes three days to reach the Moon from the Earth. It will take several months to reach the Sun and may take thousands of years to reach the nearest star. Such long distances covered in months and years are very difficult to be measured in kilometres. Therefore, scientists use units like Light Year and Parsec (PC) for measuring the distances of stars. A Light Year is the distance travelled by light in one year at a speed of 3,00,000 km. per second; it is equal to 9.4607 x 1012 km. One Parsec is equal to 3.26 light years or 30.857 x 1012 km.

It takes 1.3 seconds for the moonlight to come to us. Light from the Sun reaches the Earth in 8 minutes 18 seconds. It should take 4.2 light years for the light to reach the Earth from Proxima Centauri, the nearest star next to the Sun. The farthest star in our galaxy lies at a distance of about 63,000 light years (19.325 Parsec).

PULSARS, BLACK HOLES AND QUASARS

Pulsars

Pulsars are rapidly spinning stars that emit pulses of radio waves at regular intervals. The word ‘pulsar’ stands for ‘Pulsating Radio Star'.

When a big star explodes, its outer shell scatters to form a nebula while its core contracts into a denser star called the neutron star. Its neutrons are tightly compressed and it has extremely high density. Neutron stars are very small and dull. The average diameter of a neutron star is 10 km. These neutron stars are called pulsars.

Radio pulses coming from pulsars produce a ‘tick’ like sound on radio telescope. Neutron stars are like lighthouses in space. Ordinary pulsars flash at an interval of every one or half a second. The most rapid flashing pulsar, NP 0532 lies in the Crab Nebula and emits 30 pulses per second. The oldest and the least frequency pulsar is NP 0527 which emits pulses every 3.7 seconds. All pulsars emit pulses at a rate of one pulse per 0.03 second to one pulse per 4 seconds.

Most of the pulsars are not visible through optical telescopes. They may be observed with the help of radio telescopes. Only two pulsars -NP 0532 in the Crab Nebula and PSR 0833-35 in Gum Nebula - can be seen with the help of optical telescope. Scientists have so far discovered more than 100 pulsars.

Black Holes

When very big stars, three times bigger than the Sun, collapse by the force of their own gravity, some black regions are created in the space. These are called black holes. They have gravitational force so enormously high that no matter, not even light can escape from it.

The first black hole was detected in 1972. It was in a binary star of Cygnusx-1 which is a powerful source of X-rays. It is a small member of the binary star, which is completely black. It is not a neutron star and, therefore, it is called black hole. Normally black holes emit X-rays and infrared radiation which help in their detection in space. The mass of black holes may be equal to that of 100 million Suns.

Quasars

Quasar is an abbreviated form of Quasi Stellar Radio sources. Quasars appear like a star. Through an optical telescope they look like an ordinary dull star, but radio telescope observations have indicated that they are the source of radio waves. Quasar 3C-273 was discovered by Maarten Schmidt in 1962. The value of its redshift was 0.158. Redshift is an effect of change in frequency and is seen in moving objects. If the object is approaching, its light will shift towards the violet end of the spectrum, and if the object is moving away, its light will shift to the red end of the spectrum. Redshift indicates that the source of light was receding away.

Quasars emit radio waves and X-rays with light. The size of a quasar is 1/1,00,000 of our galaxy but its brightness is 100-200 times more. So far 12000 quasars have been discovered.

GALAXIES

At night, a milky white band of light is seen in the sky. It is called the Milky Way. Italian astronomer Galileo was the first to observe it with the help of his telescope and declared that it was a giant cluster of millions of stars. It is a galaxy. It comprises numerous solar systems and our solar system is one of its members.

Galaxies are giant clusters of stars held together by their mutual power of gravitation. Because of their vastness they are called ‘peninsulas of the universe'. Millions of galaxies may be seen with the help of a powerful telescope. They lie at a distance of 1,000 to 1,00,00,000 light years. Most of the galaxies appear scattered in the sky.

It is assumed that huge masses of gases or proto-galaxies were formed as a result of the primordial explosion in the universe and they started rotating at their own speed. Galaxies owe their different sizes and forms to their varying speed. Galaxies so far known are spiral, elliptical and irregular in shape.

Ours is a spiral galaxy. Its spiral arms are widespread. Our solar system lies near the edge of the galaxy. Our galaxy measures about 1,00,000 light years (30,600 pc). Its centre is covered under galactic dust particles and lies at about 32,000 light years (9,800 pc) from the Sun.

Our galaxy is estimated to be 12,000 to 14,000 million years old and contains around 100,000 million stars.

Our galaxy rotates on its axis - faster at the centre than at the edges. The middle part completes one rotation on its axis in about 50,000 years. The Sun and its neighbouring stars revolve round the centre of the galaxy in their orbit at an average speed of 250 km. per second.

THE SUN

The Sun is one of the stars in the Milky Way. It looks bigger than other stars because it is the closest star to the Earth. However, it is smaller than some other stars. Betelgeuse, a red giant star, is 800 times bigger than the Sun.

The Sun lies about 150 million km. from the Earth. Its diameter is about 1,400,000 km., i.e., 109 times the Earth’s diameter. Its gravitation is 28 times more than the gravitation of the Earth.

The Sun lies at a distance of about 32,000 light years from the centre of the galaxy. It takes the Sun about 225 million years to complete one revolution around the centre of the galaxy with a speed of 250 km. per second. This period is called cosmic year. The Sun, like the Earth, rotates on its axis as well. It is a gaseous mass and, therefore, can rotate at varying speeds at different latitudes. It rotates once on its axis in 24-25 days at the poles and in 34-37 days at the equator.

The Sun is composed of about 75% hydrogen and almost 25% helium. It may be called a big hydrogen bomb because it releases huge amount of heat and light as a result of nuclear fusion. The Sun is directly responsible for all life on Earth. It provides the Earth with all of its light, heat and energy.

The glowing surface of the Sun which we see is called photosphere. It has a temperature of about 6000° Celsius while the temperature of the core is 15,000,000° Celsius.

The glowing flames constantly arising from the photosphere are called Solar prominences which rise up to a height of 1,000,000 km.

The dark spots noticed on the surface of the Sun are called Sunspots. They are cooler than the surrounding area. The life span of sunspots varies from a few hours to many weeks. Larger sunspots may have temperatures up to 4000°-5000° Celsius. Some of them are made of many folded layers larger than our Earth’s size.

When sunspots persist for longer periods, they cause solar flares and high solar prominences which create upheavals in the ionosphere resulting with disturbances in our radio communications.

THE SOLAR SYSTEM

The Solar System is located at a distance of about 30,000 to 33,000 light years from the centre of the Milky Way galaxy. The Sun is a star like other stars with the only difference that it is nearer to us as compared to other stars. It has a family of its own. The Sun and its family put together is called the Solar System. The solar system consists of nine planets, their satellites, asteroids, comets, meteoroids and other debris.

Planets are heavenly bodies which, like our Earth, revolve round the Sun. They do not have their own light. They look bright as the Sun’s light falls on them and is reflected from their surfaces.

The nine planets are—Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

Mercury, Venus, Jupiter and Saturn may be seen from the Earth with naked eyes. These were known to the astronomers thousands of years ago. Three planets, namely Uranus, Neptune and Pluto were discovered later after the invention of telescope. Uranus was discovered in 1781, Neptune in 1846 and Pluto in 1930.

In the recent years, astronomers have explored the possibility of existence of a tenth planet. There is also a fair chance of discovering more moons, especially around Jupiter and Saturn.

MERCURY

Mercury is the planet closest to the Sun. It is smaller than some of the small satellites of the planets. Because of its nearness to the Sun and its small size, it is difficult to see it without a telescope but it can be seen easily immediately after sunset or before sunrise.

It takes Mercury 58.7 Earth days to make a complete rotation on its axis and 88 days to make a complete orbit around the Sun. It is the fastest revolving planet.

The distance of Mercury from the Sun does not remain constant because it has a long narrow orbit resembling a lemon in shape. It moves very slowly. Its one day is equal to about 59 days of our Earth.

One part of this planet is always in the sunlight for a longer period to raise the day’s temperature to over 350° Celsius, enough to melt tin and lead. The other part of the planet where it is night, the temperature is as low as -170° Celsius.

The pictures of the planet relayed by the space probe Mariner-10 showed that it is like the Moon. It has rocks, cliffs and craters. It has no satellite and no atmosphere.

Facts About Mercury

VENUS

You must have seen a very bright star in the evening. It is visible in the morning also. Often it is called the ‘Morning Star’ or the ‘Evening Star ‘. However, it is not a star but a planet called Venus, the one nearest to the Earth. It is the second planet from the Sun. Through a telescope it looks like our Moon. We get its full view when it is very far away from us. It is the brightest of all the planets.

Many new facts about Venus have come to light by space probes. Venus is the hottest planet in the solar system. The temperature rises up to 480° Celsius at its equator. Lead, tin and zinc melt at this temperature. Venus has very thick clouds which reach up to a height of 55 km. Thick clouds make studies of the planet’s surface nearly impossible. The temperature of clouds at the higher level drops down to -35° Celsius. This red hot planet is shrouded by icy clouds.

The atmosphere on this planet contains 90 to 95 per cent of carbon dioxide. Some hydrogen and water vapour are also present. Its surface atmospheric pressure is 100 times more than that on the Earth. No astronaut can survive in the atmosphere of Venus, nor can he tolerate its excessive heat.

Radio waves have indicated that there are mountains and valleys on this planet. The planet has no satellites. The Sun rises in the west and sets in the east on this planet.

Facts about Venus

Mean distance from the Sun: 0.72 au

Minimum distance from the Earth: 0.27 au

Planet’s day: 243 days of Earth

Its sidéral period (year): 224.7 days of Earth

Diameter: 12,104 km.

Mass: 0.82 times of the Earth’s mass

Surface temperature: 480° Celsius

Gravitation: 0.88

Density (water =1): 5.25

Main gas in the atmosphere: Carbon dioxide.

EARTH

Our home planet, Earth, is the third planet of the solar family. It is the only planet in the solar system where life exists. Earth too, like other planets, revolves round the Sun. It spins on its axis, one end of which is called the north pole and the other the south pole. One half of the Earth that receives sunlight is hot during summer while the other half has winter during that period. Thus the seasons change alternately.

Yuri Gagarin, a Russian astronaut, was the first to orbit the Earth once in his spacecraft Vostok in 1961. He looked at the Earth from space. From space or the Moon, the Earth appears full of greenery and blue water of oceans similar to that as depicted on the globe. Many of its parts hidden under the white clouds are not visible from space.

The Moon is the only satellite of Earth.

Facts about Earth

Mean distance from the Sun: 100 au

Planet’s day: 23 hours, 56 minutes and 4.09 seconds

Its sidéral period (year): 365 days, 5 hours, 48 minutes and 45.51 seconds

Diameter: 12,756 km (along equator)

Surface area: 510,065,600 sq.km.

Mass: 1

Surface temperature: 22° Celsius

Gravitation: 1

Density: 5.517 maximum density

Main gases in the atmosphere: Nitrogen, Oxygen

Satellite: 1 (Moon)

THE MOON

The Moon is the only satellite of Earth. Astronomers believe that both Earth and the Moon came into existence separately but at the same time from gases and dust remaining from the Sun’s formation. Samples of the Moon’s rocks and soil brought to the Earth by the astronauts have shown that the Moon is of the same age as the Earth and was formed about 4,600 million years ago.

The mean distance between the Earth and the Moon is 3,84,400 km. Moon’s surface area is 37,940,000 sq. km. There is a large number of craters on the surface of the Moon created by meteoroid collisions, and volcanic activity of the past. The Moon has high mountains with gentle slopes. They have neither raised sharp peaks nor steep slopes. Devoid of water and air, the Moon is unable to sustain life. The day dawns suddenly and the night also approaches in the same manner.

There is no sound either because of total absence of air and atmosphere. The Moon’s gravity is about one-sixth of the Earth’s gravity. If you can jump up to 1 metre on the Earth, you will jump upto 6.05 metres on the Moon. Similarly, an object that weights 6 kg on Earth, will weigh 1 kg. on the Moon. The day temperature rises to 120° Celsius while the night temperature drops to -160° Celsius on the Moon. On July 20,1969, the Apollo 11 astronaut Neil Armstrong became the first person to set foot on the Moon. Several other explorations from the USA followed, during which many experiments were conducted. The data obtained has vastly increased our knowledge of the Moon.

The Sun’s light falls only on one side of the surface of the Moon. The other side is always in the dark. The Moon revolves round the Earth in 27.3 days. It has no light of its own. The Moon looks bright when the sunlight is reflected from its surface. The Moon does not always look the same. Its shape keeps on changing during the month. These different shapes of the Moon are called its phases. The Moon is not visible at all when it comes between the Earth and the Sun. We have full moon when the Sun is on the other side of the Earth.

When the Earth passes directly between the Sun and the Moon, lunar eclipse occurs. It happens only on full moon nights.

The gravitational pull of the Moon causes tides. Although the Sun too is responsible for the tides, but the Moon being nearer to the Earth than the Sun, exerts greater pull on the sea.

MARS

Mars is the fourth planet from the Sun. It is about half of our Earth’s size in diameter. It is also called the red planet because of its reddish orange appearance in the sky. Like that of Earth, the axis of rotation of Mars is tilted in space and its polar regions face the Sun alternately giving it seasons of summer and winter in the northern and southern hemispheres.

Although stories have been written and even films have been made about this planet and its so-called inhabitants, the space investigations have proved that there is no life on Mars.

The pictures received from the space probe Mariner 9 indicate the existence of deep depressions, dusty valleys and raised landmasses on Mars. There are more volcanoes on Mars than on Earth. Nix Olympia, an extinct volcano on Mars, is three times more in height than Mt. Everest. Its height is 24 km. from the surface of the planet and consists of huge snow caves measuring up to 65 km. in length.

The Viking space probes (Viking-1 and Viking-2) sent to Mars in 1976 to explore the possibility of existence of life on the planet have shown that there was no life there. It is no wonder because the temperature on the planet never rises the freezing point. There is no water either.

Mars has two satellites - Phobos and Deimos. Phobos is larger than Deimos.

Facts about Mars

Mean distance from the Sun: 1.52 au

Minimum distance from the Earth: 0.38 au

Planet’s day: 24 hours 37 minutes of Earth

Sidéral period (year): 687 days of Earth

Diameter: 6,795 km.

Mass: 0.11 times of Earth’s mass

Surface temperature: -23° Celsius

Gravitation: 8.38 times of Earth’s gravitation

Density (water=l): 3.94

Main gas in the atmosphere: Carbon dioxide

Satellites: 2

JUPITER

Jupiter, the fifth planet from the Sun, is the largest planet in the solar system. It is 318 times more massive than the Earth. It is so large that 1,300 Earths could fit into it. Made up of gases, it has features of both, a star and a planet. All planets receive energy from the Sun but Jupiter spreads its radio energy, produced by explosion, in long wavelengths. This planet has the most powerful radio waves next to the Sun in our solar system.

Jupiter’s atmosphere contains mainly hydrogen and helium. Methane and ammonia are also present in traces. Its atmosphere is like that of pre-historic Earth. Hydrogen, methane, ammonia and water, which were responsible for evolution of life on the Earth, might have possibly set in motion the process of evolution of life on this planet.

The first space probe, Pioneer X, reached Jupiter at the close of 1973. It showed that the planet had magnetosphere. The radio waves coming from the magnetosphere still continue to be a mystery for the scientists, who believe that there is some life somewhere on Jupiter.

In 1979, Voyager-1 and Voyager-2 passed this planet. The closest picture of the Jupiter was taken from a distance of 1.8 million km. A 30 km. thick ring around the planet was also observed. Existence of volcanoes and elements like sulphur and oxygen on one of the satellites of the planet named Io, were also detected.

Europa, another satellite of the planet and equal to our Moon in size, is covered under ice at several places having 100 km. thick ice layers.

Jupiter is always covered under clouds. There are five bright and four dark grey bands around it. A mysterious oval-shaped red spot about three times larger than Earth is visible on its surface. It is a persistent storm that appears to be a permanent feature of the planet. It covers an area 40,000 km. long and 4,000 km. wide.

Jupiter has 63 satellites, four of which are several thousand kilometres in diameter.

Facts about Jupiter

SATURN

Saturn, the second largest planet in the solar system, is the sixth planet in terms of distance from the Sun. It is the loveliest among the planets. Like its neighbour Jupiter, Saturn also resembles a ball of gases but smaller in size. It is 95 times more massive than Earth. The magnificent ring system of this planet has made it mysterious. Spread over a distance of about 275,000 km. these rings revolve round the planet. Investigations made by space probes Voyager-1 and Voyager-2 have revealed that these rings are made up of innumerable ice-covered particles. The two Voyagers helped in measuring these particles, which have diameter of a few centimetres to 8 metres. The rings number more than 1,000.

Like Jupiter, Saturn also has a red spot on its surface although smaller in size. It contains white, elliptical and banded, light dense clouds. It is yellowish in colour.

Saturn faces very strong winds with a speed of about 1,760 km. per hour. Its surface temperature is -180° Celsius.

There are 60 known satellites of Saturn. These appear to be made up of ice. Titan, the biggest of the satellites and larger than Mercury in size, is estimated to have some atmosphere.

Facts about Saturn

URANUS

This planet was discovered by William Herschel in 1781. It is much smaller than Jupiter and Saturn but much larger than Earth. It is 15 times more massive than Earth. It looks vaguely green through the telescope. It is mainly made up of methane gas. It is a cold planet and its surface temperature drops to -210° Celsius.

Astronomers discovered in 1977 nine dull rings around Uranus, spread within a limit of 64,000 km. This is the limit wherein even a massive satellite would break to pieces by its tidal forces. As of now, there are 13 rings in all.

Uranus orbits the Sun every 84 years. Its day equals 16 hours 10 minutes of Earth.

Uranus has 5 main satellites — Miranda, Ariel, Umbriel, Titania and Oberon, with the total number being 27.

Facts about Uranus

NEPTUNE

Neptune is the eighth planet from the Sun. It was discovered by Adams and Leverrier in 1846. It is a cold planet that looks green and has a surface temperature of about -220° Celsius. It is 17 times larger than Earth. Though not yet confirmed but it is believed that like Uranus, Neptune also has rings around it. It has a day equal to 18 hours and 26 minutes and a year equal to 164.8 years of the Earth.

Neptune has two satellites - Triton and Nereid. Triton is bigger than Pluto with a diameter of 3,700 km.

Facts about Neptune

PLUTO

After the discovery of Neptune, astronomers continued their efforts in search of another planet still farther in space. It was in 1930 that C.W. Tombaugh discovered Pluto which is slightly smaller than the planet Mercury. The Sun shines over it for about 6 hours 30 minutes only. It is very cold. Its surface temperature is -230° Celsius. The Sun looks like a bright star from the surface of this planet. Pluto has no atmosphere. It is like a rocky ball.

This planet has three satellites. Its axis bisects Neptune’s orbit and therefore it is presumed to be a satellite broken away from Neptune.

Facts about Pluto

Mean distance from the Sun: 39.44 au

Minimum distance from the Earth: 28.72 au

Planet’s day: 6 days, 9 hours of Earth

Sideral period (year): 247.7 years of Earth

Diameter: 3,000 km.

Mass: 0.002-0.003 times of the Earth’s mass

Surface temperature: -230° Celsius

Main gases of the atmosphere: Frozen Methane and Nitrogen.

Satellites: 3

Note:-

From the time of its discovery in 1930 to 2006, Pluto was counted as the solar system’s ninth planet. However, with the discovery of many similar objects, on August 24, 2006, the IAU (International Astronomical Union) defined the term ‘planet’ for the first time. This definition reclassified Pluto as a member of the new category of dwarf planets along with Eris and Ceres, and given the number 134340.

ASTEROIDS

Planets and their moons are major members of the solar system. There are minor members called asteroids. An asteroid is an irregular lump of rock that orbits the Sun. They are in large numbers in a belt between the orbits of Mars and Jupiter. They lie at a distance of 2.2 to 3.3 au. This belt is estimated to have some 40,000 to 50,000 asteroids. Some of them are so tiny that their diameter cannot be measured with the help of prevalent techniques. Ceres, the biggest of these, has a diameter of 1003 to 1040 km. It was discovered in 1801. 4 Vesta, the brightest asteroid, is the only asteroid that can be seen with the naked eye. Its diameter is 555 km. Hermes, another asteroid which was at a distance of 7,80,000 km. from the Earth, is now extinct.

It is not known how asteroids came into being. Some astronomers think that they are broken pieces of some planet which once existed between Mars and Jupiter. Others consider them as pieces broken off Mars and Jupiter themselves. Some asteroids may be chips and fragments of comets.

METEORS AND METEORITES

Sometimes we see a luminous object moving very fast across the sky leaving a streak of light behind it and which suddenly disappears. It is generally called a falling star. But we know that stars never fall. These tiny bodies which appear to fall are not stars but meteors. They enter the Earth’s atmosphere with a tremendous speed and burn up as a result of frictional heating. This heat causes the meteoroid to glow. Meteors also are members of the solar system.

Meteors do not reach the Earth. Most of them either burn up and disappear on their journey or are converted into vapour and dust. Where a meteor does not burn up completely, it falls down and hits the Earth. When the meteoroid hits the Earth’s surface, it is called a meteorite.

Craters have been formed on the surface of the Moon, Mars and Mercury as a result of meteorites hitting them. The biggest such crater on Earth in Arizona was created by some meteorite. Its diameter is 1,265 metres and depth 175 metres.

Around 25 million visible meteors are estimated to enter Earth’s atmosphere everyday. They have a speed of 35-95 km. per second. An ordinary meteor takes approximately one second to convert itself into vapour. About 500 meteorites hit the surface of the Earth in a year’s period.

The largest known meteorite found in 1920 at Hoba West near Grootfontein at south-west Africa weighed about 60,000 kg. It hit the ground during pre-historic age.

Calcutta Museum has some meteorites as exhibits.

COMETS

A comet is a heavenly body with a long glowing tail of light behind it. It is also called ‘tailed star'. Long ago people feared it because they considered it inauspicious. But now people do not think that way because they have known the truth.

Comets also are members of the Sun’s family like other heavenly bodies. They have a definite orbit like that of Earth. However, they have a shape different to that of Earth. About 1,000 comets have passed by the Sun during 100 years. Of them, some are bright enough to be seen without a telescope. The most important among them is Halley’s Comet, which passes by the Sun every 76 years. It was discovered by the English astronomer Edmond Halley in 1682 and was named after him. It was last seen in 1986.

A comet has three parts - nucleus, coma and tail. Nucleus is the brightest part of the comet. It may have the diameter of 100 to 10,000 metres. The nucleus of Halley’s comet has a diameter of 5,000 metres. Composed of ice, dust and gas, the dirty snowball called nucleus shines through the centre of its head. The part surrounding the nucleus is called coma. It is made up of gases and dust and may have a diameter of more than 2 million km. Coma is surrounded by the clouds of hydrogen gas. Tail is an important part of comet. It is of two varieties - dust tail and plasma tail. The length of a dust tail may vary from 1 to 10 million km., while that of a plasma tail, composed of extremely hot ionised gases, up to 100 million km.

A comet develops the tail as it comes near the Sun. The sunlight pushes away some gas from its head. It is this gas which starts showing and looks like a tail. As the comet approaches the Sun, it rushes with a great speed along with its bright shining tail. The tail of a comet always points away from the Sun.

EXPLORING SPACE

Space age began on October 4, 1957 when Russia launched the first artificial satellite, Sputnik-1 and one month later, Sputnik-2 was launched with a dog, ‘Laika’ aboard, the first living creature in space. This suggested that human beings might survive in space.

The first US satellite, Explorer-1 was put into space on January 31, 1958. Thus, the Russian Sputniks and US Explorer pioneered the space exploration programme.

The first manned Russian satellite, Vostok-1 was put into space to go round the Earth on April 12, 1961. Vostok-1 carried Col. Yuri Gagarin, who became the first cosmonaut to complete an orbit of the Earth and to observe the Earth and the sky from space.

The first woman to go into space in 1963 was USSR’s Lt. Col. Valentina Tereshkova. She completed 48 orbits in 2 days, 22 hours and 21 minutes in Vostok-6.

In March 1965, Aleksei Leonov aboard the Soviet Voskhod-2 became the first man to walk in space.

Edward White, the US astronaut of the spacecraft Gemini 4 was the first US astronaut to make a space walk. He came out and stayed outside his craft in space for 21 minutes.

In 1965, began the series of two-manned Gemini flights. The team of astronauts for the Gemini programme practised rendezvous manoeuvres, docking procedure and space walk in preparation for the Apollo missions to the Moon.

JOURNEY TO THE MOON

The three-manned Apollo-11, which had enough space for astronauts to not only move about but also to stand erect within it, set out on a journey to the Moon on July 16,1969. The special feature of Apollo’s landing on the Moon was that its two astronauts could touch the surface of the Moon with the help of the four-legged lunar module ‘Eagle'.

SM - Service Module

CM - Command Module

LM - Lunar Module

At 10.56 p.m. on July 20, 1969, Neil Armstrong set his foot on the surface of the Moon. He was the first human being to put his foot on the Moon.

In his radio communication sent to the Earth Neil Armstrong described it as "one small step for (a) man, one giant leap for mankind". Thereafter, Edwin Aldrin stepped out on the Moon’s surface. Michael Collins remained aboard the Apollo 11 command module in orbit. The two astronauts spent around 2 hours 30 minutes on the Moon. During this period, they collected samples of Moon’s rocks and soil weighing over 20 kg.

The total estimated expenditure on this US space programme at sending men to the Moon, with Apollo 17 was around 2,554.1 million dollars. With a view to reduce expenditure ‘space shuttle’ was invented by the US scientists. Space shuttle is a reusable manned space vehicle with a speed of about 28,000 km. per hour. The first space shuttle Columbia was launched on April 12, 1981. The USSR launched a similar space vehicle named Buran in September 1988 which returned to the Earth safely after successfully completing the mission.

After the success of this mission, the following persons made journey to the Moon under the Apollo programme. They brought with them rocks and soil weighing 3,800 kg.

Apollo 12; Conrad, Bean, Gordon November 14, 1969

Apollo 14 : Shepard, Mitchell, Roosa January 31, 1971

Apollo 15 : Scott, Irwin, Worden July 26, 1971

Apollo 16 : Young, Duke, Mattingly II April 16, 1972

Apollo 17 : Cernan, Schmitt, Evans December 7, 1972

@ It is an astronomical unit representing mean distance between the Earth and the Sun. It is equal to 149,598,500 km.

02

EARTH

ORIGIN OF THE EARTH

The earth is one of the nine planets of the solar system and revolves around the sun through space. It has all the favourable conditions required to sustain life. The earth is the only home for human beings, animals, plants and other organisms. Scientists theorise that the earth was born around 4.6 billion years ago out of the clouds of dust and gases. However, before coming into the present shape, it was a fire ball surrounded by the clouds of hot gases. It took millions of years to cool down and the envelope of hot gases turned into clouds. These clouds rained for a long time and the rain water accumulated in the low lying areas of the earth which after a long time turned into oceans of today. In the beginning, the earth was a giant land mass called Pangaea. This land mass gradually split into different land masses which are called continents today.

Mountains and volcanoes have resulted due to the upheavals in the interior of the earth. In the process of cooling, the upper surface of the earth became solid which we call as the earth’s crust. About 570 million years ago, the life began on the earth in the form of micro-organism. The first 345 million years saw the development of aquatic life. For the next 160 million years reptiles came into existence and subsequent 65 million years saw the development of mammals. The development of man is an event of one million years old but we know about its existence for only 10,000 years ago.

EARTH AND THE ATMOSPHERE

Inside the earth

According to scientific studies, the earth from the top to centre can be divided into three parts: Crust, Mantle and the Core. Core is further subdivided into outer core and inner core.

The outer skin of the earth is called crust. The thickness of the crust varies from 5 to 10 km under the oceans and to about 30 to 40km under the continents. The crust is made up of three kinds of rocks — igneous, sedimentary and metamorphic. Beneath the earth’s crust are the mantle, the outer core and the inner core. The mantle is a thick layer of solid rocks and goes down to about 2900 km. The rocks in the mantle are made up of silicon, oxygen, aluminium, iron and magnesim. Its temperature increases from 870°C to 2200°C as we go down. The outer core is about 2200 km thick and is made of melted iron and nickel. Its temperature ranges from 2200°C (upper most part) to 5000°C (deepest part). The ball shaped inner core is about 5150 km below the earth’s surface. The centre of the inner core is about 1200 km below the inner boundary of outer core. It is made of solid iron and nickel.

Atmosphere

The envelope of air which surrounds the earth from all sides is called atmosphere. The atmosphere is held due to the gravitational pull of the earth. The outer layer of the atmosphere is called the Exosphere which extends up to an altitude of 2000 km above the sea level.

All gases of the atmosphere combined together constitute air. Atmosphere contains 78% nitrogen, 21% oxygen and remaining 1% consists of argon, carbondioxide, neon, helium, ozone and hydrogen. Air also contains water vapour and particles of dust.

In the lower layers of the atmosphere, the ratio of different gases remains relatively constant but the percentage of water vapour goes on changing. Clouds float in the lowest part of the atmosphere called Troposphere. The air gets thinner, as we go above the surface of the earth. The atmosphere has many parts such as the Troposphere, Stratosphere, Mésosphère, Inosphere and Exosphere.

LITHOSPHERE OR CRUST

The uppermost layer of the earth is called litho-sphere or the crust. Its average thickness is 30 km to 40 km under the continents, 5 km to 10 km under the ocean floor and upto 60 km under the mountains. At certain places below the pacific floor, its thickness is very little. The earth’s crust consists of two layers — the upper layer and the lower layer. The upper layer is called SIAL (silicate + aluminium). It is made up of granite-like rocks which mainly consist of silica and alumina. Below the upper layer lies the lower layer called SIMA (silicate + magne-temperature prevails in this region. It is the same material of which the rocks on the surface of the earth are made.

There are three kinds of rock structures in the upper continental crust of the earth. Of them, the most abundant are the Pre-Cambrian crystalline shields. In the second place are the coastal areas formed of sedimentary rocks. The structures of the third part are folded mountains.

The crust of the earth is made up of a number of plates — large in size and of varied thickness, called the crustal plates. Some of them are in the form of ocean floor while others are in the form of continents. Earthquakes occur due to the upheavals of these plates.

CONTINENTS

A little less than one-third of the earth’s surface is land mass and the rest is covered by water. There are seven large continuous land masses called continents. They are: Asia, Europe, Africa, North America, South America, Australia and Antarctica.

According to the German Geologist, Alfred Wegener, once, the earth was a single land mass known as Pangaea. Nearly 200 million years ago, this land mass broke into two parts — Laurasia and Gondwana land.

According to Wegener’s Continental Drift Theory, these two large land masses continued to drift away from each other. Present North America and Eurasia (Europe and Asia) emerged out of Laurasia, while the South America, Africa, Australia and Antarctica owe their existence to the Gondwana land. Thus the seven continents of the world appeared.

The theory also explains that not only the continents but also the crust plates, which include both the continents and the oceans, drift. Thus the continents are undergoing changes even now. Infact, earthquakes are also caused due to the drifting of these crust plates.

ROCKS

The rocky crust of the earth is made up of three kinds of rock formations: igneous, sedimentary and metamorphic rocks.

Igneous rocks are made up of hot magma. The magma that is pushed out due to volcanic activities forms igneous rocks on cooling. Igneous rocks are the oldest rocks found on the earth. The main igneous rocks are granite, basalt and volcanic rocks. The volcanic rocks are formed of the hot liquid lava thrust out from the valcano.

Sedimentary rocks are made up of deposits of grains of rocks, shells and skeletons under the sea bed. Coal also is a sedimentary rock formed as a result of the forests buried under swamps in the ancient times. Limestone, gypsum, sandstone and clay are the examples of sedimentary rocks. Igneous rocks account for 95% and sedimentary rocks 5% of the volume of the earth’s crust.

The metamorphic rocks are formed by the actions of heat and pressure on igneous and sedimentary rocks. Marble is a metamorphic rock that is formed as a result of action of heat on limestone. Similarly, clay is transformed into slate. Precious minerals like garnets and rubies are found in several metamorphic rocks. Rocks are very useful for us. Marble is obtained from rocks which is used for making the statues of gods and goddesses and are also used in the construction buildings, temples, etc. The stones that are derived from these rocks are used in building, roads. The clay transforms into slate widen is also used in the construction of buildings.

EARTHQUAKES

Earthquake produces tremors or vibratory shocks in the earth. Sometimes the tremors are so weak that people cannot feel them. But at times, they are so violent that long cracks are formed in the earth’s crust, buildings collapse, monuments topple, and people perish. Many sudden tremors and shocks felt in the earth’s crust are called earthquakes.

There are many reasons behind earthquakes. According to seismologists, the outer layer of the earth is made up of many thick plates. All these plates are in slow, continual motion with respect to each other. Currents within the hot, molten interior of the earth, produced by thermal convection and the earth’s rotation, are thought to underlie plate movement. In some areas the plates are being driven apart as new molten material is forced upward between plates. In other region, the plates slide past each other. In a third kind of situation, plates push direclty into each other, causing one plate to slide beneath the other. The difference in motion between plates, causes rocks to fracture along cracks, creating earthquakes.

A few local earthquakes are volcanic in origin. These are produced by movements of underground molten magma straining and fracturing adjoining surface rocks. In many places tremors have been felt as a result of deep digging by man.

The areas prone to earthquakes are known as seismic belts. Assam in India is one of the world’s most earthquake-prone areas. The instrument used for the study of earthquakes is called the seismograph. Richter scale is used for recording the intensity of earthquakes. The Indian Institute of Technology (HT) at Roorkee has a seismo graph. However, it is very difficult to predict an earthquake.

MOUNTAIN FORMATION

Most of the mountain ranges have been formed due to major changes that have taken place in the earth’s crust over the ages. They are classified in four categories on the basis of the process of their formation. The four categories are: fold mountains, block mountains, residual mountains and volcanic mountains.

Fold mountains are made up of many layers or rocks. They are formed due to violent contractions and pressure inside the earth. Because of this, the rocks turn wavy and overlap each other and their layers get folded to rise above the earth’s surface to form mountains. The Himalayas, the Andes, the Rockies and the Alps came into existence as a result of folding process.

Mountains formed by vertical faults are called block mountains. Great blocks of rock are uplifted above the surrounding terrain because of vertical movements along faults. The mountains rise as great tilted blocks. The Vosges in France and Black Forests in Germany are the examples of block mountains.

Residual mountains are formed due to denudation and erosion by which high plateaus are gradually shaped into peaks and ridges. Denudation and erosion is caused by natural agents such as wind, water, snow, etc. The Catskill range in the southern New York state is an example of residual mountains. The Grand Canyon in Arizona, USA, is the result of erosion by Colorado.

Volcanic mountains are formed due to the accumulation and solidification of lava, ash and debris erupted from the earth’s interior. They are basically cone shaped with a crater at the top. The Fujiyama in Japan is an example of volcanic mountains. (See Volcanoes) Hood and Rainier of America are also example of such mountain ranges. The hight of the mountains increases only a few millimetres every year.

FOLDS AND FAULTS

Continuously operating internal and external forces influence, alter and give new shapes to the earth’s crust.

The internal forces cause the slow or secular movements lasting for millions of years as well as the sudden movements like earthquakes. The slow movements are responsible for folding and faulting which give birth to mountains, plateaus and rift valleys.

Fold

Folding is a process which produces bends or folds in rock. Folding is caused by great compressional (side ways) forces acting on layers of rock in the earth’s crust.

Folds are of various kinds such as symmetrical fold, asymmetrical fold, monoclinal fold, overfold, recumbent fold and nappe.

Faults

When the rocks within the earth’s crust break and move apart due to tension and compression, it is called faulting. Faults can move horizontally or vertically from a few centimetres to many kilometres.

Faults are mainly of three kinds — Normal faults, Reversal faults and Tear faults.

Faults shape the landscape by their movements. When rocks on one side of the fault shift vertically, a ridge is formed on the uppermost surface. A block of land that rises between the two faults is called a horst. A large garben between two faults is called a rift valley. The Black Forest Mountain of Germany is of this type.

VOLCANOES

The mountains which throw up fire, smoke and cinder are called volcanoes. When volcanoes erupt, the magma (melted rock) reservoir in the layers of the earth’s interior forces itself out through the crust to the surface of the earth. The liquid substance that is forced out as a result of volcanic eruption is called lava. The lava is a mixture of hot volcanic cinder, pieces of rocks and steam. The number of active volcanoes on the earth is estimated from about 500 to over 800. Most of the volcanoes are funnel or cone shaped. Their mouth is called crater. The crater is connected to a pipe-like opening through which magma from the earth’s interior is thrown out. By the action of the gases and steam accompanying the magma, the rocks at the top and slopes are blown up to form a hole. Mt Fujiyama, in Japan, is an example of such a volcanic mountain. Some volcanoes have dome like tops. They are called shield volcanoes. Mauna Loa in Hawaii Island is an example of shield mountain.

On the basis of the amount of their activity, the volcanoes are classified as (i) active, (ii) dormant and (iii) extinct. An active volcano is always erupting. Hawaii Island’s Mauna Loa and Sicily’s Mt. Etna are examples of active volcanoes. A dormant volcano is temporarily inactive. Examples of such volcanoes are Mt. Fujiyama in Japan and Mt. Vesuvius in Italy. An extinct volcano remains completely inactive for hundreds or thousand of years. Mt. Kilimanjaro in Africa and Mt. Aconcagua in South America are examples of extinct volcanoes. The world’s highest extinct volcano is in Argentina Which is about 6960 metres high.

Volcanic eruptions sometimes cause large scale destructions. Pompeii and Herculneum were buried under eruption from Visurius. Volcanic eruption in 1883 blew off two-third of Krakatoa island of Indonesia. It was the greatest explosion during the last 3000 years. The magnitude of this explosion was equal to that of 1500 megaton of TNT and it was heard as far as 500 kilometres. Besides this, the explosion resulted in tidal waves in all the seas and oceans across the globe.

A volcano is a vent or fissure in the earth’s crust through which hot solids, gases, smoke and liquids emerge out violently. A volcano also refers to the mountain that forms around the hill.

DESERTS

A desert is a barren region that has vast expanses of sand. Which is yellowish in colour. It receives very little rainfall. In deserts, only a few varieties of plants and animals can exit. These are those species that require little water. They can survive for a long time even without water. In most deserts, days are very hot but the nights are cold.