Revolutions and Wars of Independence

American War of Independence Great Britain regulated trade in the American colonies to such a great extent that there was growing annoyance among the settlers at the controls and checks imposed upon them. There were acts of rebellion and this hostility flared into war on 19 April, 1775; when shots were exchanged in Lexington. The first battle of the war was fought at Bunker Hill Charlestown in which Britain won; they also scored decisive victories in New York (1776) and Philadelphia (1777). But the American Continental Congress had appointed George Washington (1732-99) to take charge of the untrained American soldiers and he inspired them to fight for their freedom. Further inspiration was provided on 4 July, 1776 when the Congress issued the Declaration of Independence drafted by Thomas Jefferson. The Declaration renounced allegiance to the British throne and resolved "that these United Colonies are, and of right ought to be, free and independent states.'' Americans were aided in their fight by Britain's enemies in Europe and in 1777 the British general Burgoyne (1723-92) was forced to surrender at Saratoga. In 1781 General Cornwallis (1738-1805) besieged at Yorktown by French ships which prevented aid from reaching him by sea, surrendered and the War of Independence ended. America was granted its independence in 1783 and George Washington was elected the first President of USA. Boston tea party – It is an incident related to the War of Independence in America when settlers in colonies threw a shipment of 342 chests of tea into the sea at Boston in 1773. To suppress the agitation, the colony of Massachusetts was brought under direct control of the Crown. Greek War of Independence The Turkish empire included south-east Europe and the Middle East. The Greeks were the first people to revolt against the Turks in 1821. Russians supported the Greeks, Britain and France also joined in supporting the Greeks in 1827. All three countries joined together to destroy the Turkish empire and the Turks were forced to yield. The Greeks achieved independence in 1830. Belgian War of Independence (1830) When the Dutch gained independence in the late sixteenth century, the southern provinces of the Netherlands (roughly equal to modern Belgium) remained under the rule of Spain, and later Austria. During the Napoleonic, wars they were overrun by the French and when Napoleon was defeated in 1814 Belgium was reunited with the Netherlands as one kingdom. The union with the Dutch was not accepted in Belgium. Although the two peoples had much in common, problems arose out of differences in religion, language and social customs. Under the Dutch king the Belgians, felt that they were being regarded as second-class citizens. This led to riots against Dutch rule in 1830 and quickly developed into a full-scale mass revolution. The Belgians declared their independence in 1830 and drew up a national Constitution in 1831 inviting Leopold of Saxe-Coburg (1790-1865) to become their first king. French Revolution (1789-1793) In the 18th century France was under the despotic rule of King Louis XVI, who was not only inexperienced but also weak, feeble and lacked administrative capabilities. He believed in the Theory of Divine Right of Kings. At the time French society consisted of nobles, clergy and the commoners. Nobles belonged to the highly privileged class and enjoyed special rights. As one-fifth of the land was the property of the church, the clergy monopolized offices of the church and led a luxurious life. The commoners were isolated as the most under-privileged class which comprised peasants in villages, workers in cities and middle-class government employees. The commoners were awakened by French philosopher of the time who attacked the church, the crown, and old traditions, of despotic rule. Montesquieu (1689-1755) who was dead against the Divine Right Theory of kings; Volatire (1664-1774) who exposed the tyranny and arbitrary practices of the King, abuses of the Church and social inequalities; Rousseau (1712-1778), were the 18h century philosophers of France, who through their writings and ideologies of liberty, equality and fraternity prepared the nation for this great revolution in France. French Revolution not only made France a Republic but also gave new direction to the oppressed people of other countries, helped advocated and furthered the cause of liberty, fraternity and equality by awakening people against despotic rulers in their countries. Russian Revolution (1917-1922) The great revolution in Russia took place in two stages. The first stage of the Russian Revolution began in February 1917 with the overthrow of the Czar Nicholas II. The second stage in October of the same year led to the establishment of the world's first communist state by the Bolsheviks under Lenin. Revolution Russia joined the Allies in World War I to 1914, and met with success in the beginning but was defeated in 1915-16 with over 5.5 million casualties in 2.5 years of war. This led to shortage of war material and food which thoroughly frustrated the soldiers. On 7 March, 1917, workers struck work and attacked Petrograd. Farmers revolted to villages and the frustrated soldiers of World War I joined the general public to revolt against the Czar. Riots broke out and lawlessness spread throughout Russia. The Czar was dethroned and a temporary government set up under prince Kerensky's leadership. Kerensky was the follower of a midway policy (Mensheviks group) but people wanted definite social and economic changes. Lenin who was deeply influenced by the principles of Karl Marx took over leadership of the Bolshevik party which wished to setup a common government. The unity of labourers and peasants under the leadership of Lenin made the revolution a success. Lenin emerged as a great revolutionary leader; Czar Nicholas II and his family were assassinated, power came into the hands of the public, and landlords, traders and the clergy were reduced to destitution. The Russian revolution set up a new society on the basis of communist principles and thus the great revolution came to an end. This was a great revolution after the French revolution (1789-93) which was not limited to Russia alone but affected almost all countries of the world. It established the ideology of Marxism and led to the independence of several countries. Chinese Revolution The Manchu Dynasty was overthrown and a republic proclaimed in October 1911. First President Sun Yat-Sen resigned in favour of strongman Yuan Shih-Kai. Sun organized the Parliamentarian `Kuomintany' Party. Students launched protests on 4 May, 1919 against League of Nations concessions in China to Japan. Nationalist, liberal and socialist ideas and political groups spread. The Communist Party was founded in 1921. An Communist regime took power in Mongolia with Soviet support in 1921. Algerian War of Independence (1947-62) In 1947 Algeria became politically unified with France but the 86 percent Muslim population (Arabs and Berber) revolted against French domination and in 1954 war broke out. French deployed half a million troops against the rebels, but instead of suppressing the revolution, troops supported the agitation and it turned into a sort of civil war. General De Gaulle was called upon and he ultimately planned the Algerian independence which was achieved in 1962. Creation of Bangladesh Elections in Pakistan in 1970 resulted in a split between the Punjabis of West Pakistan and the Bengalis of East Pakistan. By March 1971 the tension between the two groups had escalated. Sheikh Mujibur Rahman (1920-75) of East Pakistan and his separatist party the Awami League launched a civil disobedience movement and called for independence from Pakistan's rule. On Pakistan's Republic Day (March 23) people dragged down its national flag and unfurled the flag of Bangladesh. Severe fighting took place between the separatist (Mukti Bahini) and Pakistan's forces stationed in East Pakistan. Mujibur Rahman was charged with treason. However, formal independence was declared on 17 April, 1971 and fierce fighting continued in which India supported the separatist group. Sheikh Mujibur Rahman was nominated President of Bangladesh while in jail and returned to Bangladesh in January 1972 to a tumultuous welcome. He was, however, assassinated in 1975. Collapse of the Soviet Empire In 1985 President Gorbachov inherited a collapsing empire. Constricted by domestic pressures, he chose not to intervene when, in a few dramatic months of late 1989 and early 1990, communist governments of Eastern Europe collapsed under popular pressure and new regimes declared themselves independent of Soviet control. The tearing down of the Berlin Wall, and subsequent reunification of Germany was the most powerful symbol of change. The situation was little better in the republics which constituted the Soviet Union. The people were increasingly disillusioned by falling living standards and inefficient government. Powerful nationalists forces, from the southern republics of Armenia to Azerbaijan to the old Baltic States in the north, now threatened to break up the Soviet Union from within. In August 1991 an attempt by communist `hard-liners' to restore the old system in a coup d'etat failed, leaving the central Soviet government stripped of any real power. As one republic after another announced succession it was quickly clear that the world possessed another `sick man'<197>with all the attendant dangers. The collapse of Soviet Union signaled the end of superpower confrontation.

World War I (1914-18)

(1) Germany has become a great industrial country and wanted to have more markets for trade. (2) Germany was jealous of the colonial and naval greatness of England. William II, Kaiser of Germany, was very ambitious and wanted to gain influence in Turkey by linking Berlin with Baghdad by a railway line. This gave rise to great rivalry between England and Germany. (3) The immediate cause of the war the murder of Archduke Ferdinand (the
heir to the throne of the Austrian Empire) at Serajevo by a Serbian. The Austrian held the Government of Serbia responsible for the murder and ultimately attacked Serbia.

Germany, Austria, Hungary, Turkey and Bulgaria were on one side and, were called Central Powers. England, France, Serbia, Belgium, Japan, Russia were on the other side,
and were called the Allies. Italy in 1915 and the U.S.A. in 1917 joined the Allies against the Central Powers.

The war started on the 4th August, 1914 and ended on 11th November,1918.

World War II (1939-45)

(1) By the Treaty of Versailles which ended World War I, Germany was not only dismembered, disarmed but also himiliated, and very exacting conditions were imposed
upon her. (2) There was strong feeling of deep social discontentment in Germany and Italy after the War. (3) The rise of the Nationalist movement in Germany and Italy; and the growing power of the Nazis under Hitler and that of the Fascists under Mussolini seriously upset the balance of power in Europe. (4) The colonial and commercial rivalry between England and France on one side, Germany and Italy on the other, brought them into conflict with each other. (5) Germany had become very aggressive, she annexed the Saar Valley, occupied Rhineland and Austria : Captured Czechoslovakia, etc.

The immediate causes were that Germany gave an ultimatum to Poland regarding (i) surrender of the Port of Danzing, (ii) the right of establishing rail link between Germany and East Prussia, through the Polish Corridor. These two demands were rejected by Poland, so Germany invaded Poland on 1st September, 1939. Britain and France as
they were under treaty obligations to aid Poland, declared war against Germany on 3rd September, 1939. Germany, Italy and Japan, called the Axis Powers, fought on one side;
U.K., U.S.S.R., France, U.S.A., Benelux countries, etc., called the Allies, fought on the other. It ended on 14th August, 1945.

Landmarks in World History

Magna Carta

The Magna Carla was a Charter of Rights granted to the Englishmen during 1215 AD by King John II. During the reign of King John II (1167-1216) the citizens of Britain were burdened with heavy taxes. As a treacherous and cruel king he curbed the privileges of nobles and clergymen. As a result the barons, clergy and the common people united and compelled King John to redress their grievances by signing the Great Charter known as the Magna Carta. It was signed by King John II in June 1215 at Runnymede. The charter contained 63 clauses guaranteeing the freedom of the barons, the church and the common man. Under this charter the king himself was to act according to the law which curbed the king's right to levy taxes arbitrarily. It ensured that the king would act with the sanction of the people's representatives in the matters of administration be it the imposition of new taxes or punishing a wrong doer or imprisonment of any man. In other words, through this document the Law was made the highest authority in the land. The Magna Carta laid down the important principle that England should be governed by a definite law and not by the whims or will of a despotic ruler.

Feudalism

Feudalism was apolitical and economic system of medieval Europe based on the relation of lord to vassal in which land was held on the condition of homage and service. A lord would promise to protect a smaller landowner from his enemies. In return, the small landowner or peasant surrendered his land and became a vassal. In 888 AD big empires were divided into small kingdoms of landowning nobles who protected peasants against tribal attacks. Peasants surrendered their lands to the nobles for protection of their lives. They were allowed to work and live on it but the land became feudal property. Feudal lords became rich and powerful and kings had to depend on them for men and money.

Renaissance

Renaissance means revival or rebirth. During the time of the Roman empire all the manuscripts containing the wisdom of the ancient Greeks were kept in Constantinople and studied by the scholars of the city. However, in 1451 AD a new Sultan, Mahomet II ascended the Turkish throne and swore to capture Constantinople (now Istanbul). In 1453 he attacked and occupied the city. The scholars fled taking with them the manuscripts and documents and settled in the cities of Italy to spread their learning throughout western Europe. In 1454, Gutenberg set up a printing press and these manuscripts and documents were reprinted, and thus astronomy, geography and other sciences were rediscovered by western Europe. A Greek copy of the New Testament (Part of the Bible) was also found, which revolutionized the process of religious reform in Europe. The Renaissance has been called therevival of learning that swept across Europe. The movement slowly spread to England in the 15th and 16th centuries.

Habeas Corpus Act, 1679

The Habeas Corpus Act was drawn up during the reign of King Charles II which stated that no one was to be imprisoned without a writ or warrant stating the charges against him. It also provided facilities to a prisoner to obtain either speedy trial or release on bail. The Act safeguarded the personal liberties of the people against arbitrary imprisonment by the king's orders.

Glorious Revolution

King James II of England, became very unpopular due to his strong Catholic beliefs. As a result he was forced to flee to France. The government invited William of Orange (1650-1702) the Dutch leader and his wife Mary, daughter of King James II, and declared them joint sovereigns on 13 February, 1689. The overthrowing of James II was without any bloodshed and is thus known as the Glorious Revolution.

World Civilizations

Egyptian Civilization

It is one of the world's longest continuous civilizations. In 300 BC Upper and Lower Egypt were united, beginning a period of cultural glory and native rulers that lasted nearly 3,000 years. Historians have divided the history of Egypt into the Old, Middle and New Kingdoms, spanning 31 dynasties and lasting to 322 BC. The highlight of the Old Kingdom was the building of the pyramids of Giza. The Middle kingdom saw Egypt develop into a great power. Massive temples and tombs, such as Tutenkhamun's were built during the New Kingdom. Another classification is the pyramid age (3490-2500 BC), the Feudal Age (about 1800 BC), the New Empire (about 1150 BC). In the fourth and third millennium, the Pharaohs held supreme power. The Egyptians studied nature with great care. They were aware of five planets. They divided the day-night cycle into twelve hours. They also developed a system of writing called hieroglyphics.   Mesopotamian Civilization Mesopotamia was the ancient region between Tigris and Euphrates in South-West Asia, roughly corresponding to modern Iraq. It was the site of one of the earliest human civilizations, resulting from the development of irrigation in the 6th millennium BC and the extreme fertility of the irrigated land. Sumerians settled in the lower parts of Tigris and Euphrates valley between 5000 and 4000 BC. Its seat was the city of Mesopotamia, founded by the Sumerians Babylonia gained supremacy in the 18th Century BC and was followed by others, notably the Assyrians. Later ruled by the Persians Greek and Romans, Mesopotamia gradually lost its distinctive cultural traditions. Mesopotamia bears the stamp of clay as does no other civilization, and nowhere in the world but in Mesopotamia and the regions over which its influence was diffused was clay used as the vehicle for writing. They also created mythological and historical epics like the famous 'Creation' and 'Flood Epics'. The most impressive work of the Babylonians is the 'Epic of Gilgamesh' containing their main myths. Chinese Civilization The first documented dynasty was the Shang (c. 1523-c. 1020 BC), when bronze casting was perfected. The Zhou dynasty (c. 1030-221 BC) was the age of Chinese Classical Literature, in particular Confucian and Lao Tzu. China was unified by Qin Shihuangdi, whose tomb near Xlan contains the famous terracotta army. The majority of the great wall was built by the Qin dynasty (221-206 BC). The Ran dynasty established in 206 BC and ruled until AD 220. The Ran dynasty developed the empire, a bureaucracy based on Confucianism, and also introduced Buddhism. China then split into three kingdoms (Wei, Shu and Wu). Tang dynasty (618-907) was a golden era of artistic achievement, especially in poetry and fine art. Genghis Khan conquered most of China in the 1210s and established the Mongol empire. Kubla Khan founded the Yuan dynasty (1271-1368), a period of dialogue with Europe. The Ming dynasty (1368-1644) restablished Chinese rule and is famed for its fine porcelain. The Manchu Qing dynasty (1644-1912) began by vastly extending the empire.   Greek Civilization The earliest urban society in Greece was the palace-centered Minoan civilization. It reached its height on Crete c. 2000 BC. It was succeeded by the mainland Mycenaen civilization, which arose c. 1600 BC following a wave of Indo-European invasions. A second wave of invasions in c. 1200 BC, destroyed the Bronze Age cultures, paving the way for a dark age. Classical Greece began to emerge (c. 750 BC) as a collection of independent city-states including Sparta and Athens. The civilization reached its heights, after repelling the Persians at the beginning of the 5thcentury BC and began to decline after the civil strife of the Peloponnesian war. The Greek city-states were taken over by Philip II of Macedon in 388 BC. Greek culture was spread by Philip's son Alexander the Great throughout his empire. In the 2nd century BC, the Romans conquered Greek city-states. The Greeks were the first political scientists and democrats in the world. Greece occupies a great place in the history of world civilization. The outstanding philosophers like Socrates, Plato and Aristotle were the products of this civilization. The Greeks also built many temples. Homer's 'Iliad' and 'The Odyssey' are also Greece's great gifts to the world.   Roman Civilization Rome is situated on the river Tiber in Italy. Etruscan traders occupied this city and made it the largest and most important cities of central Italy. Between 338 and 169 B.C., the Romans dominated the Mediterranean world. Between 167 B.C. and 14A.D. much of the land was conquered, the republic was brought to an end and the Roman Empire was established. The rise of Caesar is a remarkable event in the Roman history. After Caesar, Octavian brought the republic to an end. The ancient Romans worshipped their family deities. Galen, a physician, completed an encyclopedia of medicine. Caesarian Operation, first tried at the birth of Caesar became popular. In the fourth century after Christ, Theodosius made Christianity the religion of the state.

THE PLANETS

THE PLANETS

The bodies revolving around the sun (at the same time rotating on their imaginary axis) are called planets. They have no light of their own but shine by radiating the fight they receive from the sun. They all revolve around the sun in elliptical orbits. Until about 200 years ago only six planets were known. Three more planets were discovered later, the latest being Pluto (discovered in 1930). Nine planets can now be identified. Mercury Mercury is the planet nearest to the sun. It rotates on its own axis in 56.65 earth days. It takes 88 days to complete one revolution round the sun. Thus it is the fastest planet in our solar system. Venus Also known as the evening star and morning star, is the brightest object in the sky after the sun and the moon. It is slightly smaller than the earth and is the planet closest to the earth. It is also the hottest planet in our solar system and has a weak magnetic belt. Mars Mars is the fourth planet from the sun and is the next planet after the earth. Being favorably situated, it is brighter than most of the stars and, is therefore, known as the Red Planet. It has two small satellites called Phobos (Fear) and Deimos (Terror). Jupiter Jupiter is the largest planet in our solar system. It is about eleven times larger than the earth. Its volume is one and half times the volume of all the planets combined together. The most conspicuous aspect about Jupiter is its Great Red Spot. It is also known as the giant planet because of its huge size. Saturn Saturn is an outer planet visible to the naked eye. Second in size to Jupiter, it is the least dense of all the planets. The most spectacular feature of Saturn is its system of rings. The ring system is made up of a variety of separate particles which move independently in circular orbits. It has 46 satellites. Titan is its biggest. Uranus Uranus is the seventh planet from the sun and is not visible to the naked eye. It was identified as a planet in 1781 by William Herchel. It has completed only two revolutions round the sun since its discovery, and takes about 84 terrestrial years to circle round the sun. It has 27 satellites. Neptune Neptune is not visible to the naked eye but can be seen through a small telescope as a greenish star. It is eighth in position from the sun. This planet was discovered by J.G. Galle of Berlin in 1846. Till 1930, it was believed to be the farthest planet from the sun and the outermost in our solar system. It has eight satellites, and Triton and Nereid are the most con­spicuous of them. Pluto Pluto is the youngest planet to be discovered in our solar system. It was discovered photographically by C.W. Tombaugh (USA) in 1930. It is the smallest planet in our solar system; slightly smaller than Mercury and visible only through a tele­scope. The duration of its revolution round the sun is the longest and it is, therefore, the slowest planet in our solar system.

SATELLITES

Satellite are bodies which revolve around the planets. All planets have one or more satellites, except Mercury and Venus. The moon is the earth's natural satellite. There are approximately 62 satel­lites in our solar system. In August 1989, the US Space probes Voyager-1 and Voyager-2 revealed six new satellites around Neptune which was earlier believed to have only two satellites. The Moon The moon is the earth's natural satellite and is its nearest neighbour in space. It revolves around the earth while rotating on its own axis. Only 59% of its surface is directly visible from the earth. Of all satellites in the solar system, the moon is the largest in proportion to its primary body, that is, the earth. All other satellites have sizes below 1/8 the size of the mother planet. The moon is about 1/4 the size of its mother planet, the earth. It takes about 1.3 seconds for moonlight to reach the earth, whereas sunlight takes about 8 minutes and 16.6 seconds to reach the earth. The moon takes 27 days 7 hours 43 minutes and 11.47 seconds to complete one revolution of the earth. It rotates on its axis in exactly the same time. Hence, we see only one side of the moon.

THE EARTH

Modern theories on the formation of the Earth and other planets are of course based on the Copernican theory. The age of the Earth was a matter of speculation till very recent times. It was only about 200 years ago, that scientific enquiries were started by geologists. According to their deductions, based on the study of rocks, the age of the Earth is 4.6 billion years. Our knowledge of the internal structure of the Earth is derived from studies of earthquakes. The shock waves sent out by an earthquake indicate the physical nature of the regions through which they pass. These studies show that the centre of the Earth is a solid core–the Inner Core. The density of this core is about 13 g to the cubic centimeter. The Inner Core is about 1,370 km thick and is surrounded by an Outer Core of around 2,080 km. The Outer Core appears to be molten. The Outer Core is surrounded by the Mantle which has a thickness of around 2,900 km. The Mantle is topped by the crust of the Earth, which varies widely in thickness–from 12 to 60 km. At the centre or the Inner Core, that is at a depth of some 6,370 km, temperature goes upto some 4,000°C and pressure reaches nearly 4 million at mospheres. The mantle is important in many ways. It accounts for nearly half the radius of the Earth (2,900 km), 83% of its volume and 67% of its mass. The dynamic processes which determine the movements of the crust plates are powered by the mantle. Starting at an average depth of from 45 to 56 km below the top surface of the Earth, the mantle continues to a depth of 2,900 km where it joins the outer core. The mantle is a shell of red hot rock and separates the Earth's metallic and partly melted core (both the inner and the outer cores) from the cooler rocks of the Earth's crust. It is composed of sllicate minerals rich in magnesium and Iron. The density of the mantle in­creases with depth from about 3.5 gram per cubic centimetre to around 5.5 gram, near the outer core. The outer surface of the Earth is divided into 4 spheres: Lithosphere means the entire top crust of the Earth and includes not only the land surface but also the ocean floor. Hydrosphere is the water sur­face which includes the oceans, lakes and rivers. Atmosphere is the blanket of air that envelops the Earth. It covers both the land surface and the water surface. Biosphere is this sphere of life which spreads over all the three other spheres. Earth's Movements The earth has two types of move­ments, viz. rotation or daily motion and revolution or annual motion. The earth spins on its own im­aginary axis from west to east once in 24 h (in precisely 23 h 56 min and 40.91 s). It is also called diurnal or daily motion. The axis is an imaginary line which runs form north to south and passes through the centre of the earth. It always remains in­clined at an angle of 66½° to the plane of the earth's orbit. Effects of Rotation: (i) Occurrence of day and night. (ii) The position of a place on earth can be fixed. (iii) Change in the direction of wind and ocean currents.

ECLIPSES

When the light of the sun or the moon is obscured by another body the sun or moon is said to be in eclipse. Lunar Eclipse: The moon is said to be in eclipse when the earth comes between the moon and the sun, and this is called Lunar eclipse. The shadow cast by the earth on the moon is called an eclipse. Lunar eclipse occurs only on a full moon day. However, it does not occur on every full moon day because the moon is not in the same position in relation to the earth and the sun on every full moon day. Solar Eclipse: The sun is said- to be in eclipse when the moon comes between the sun and the earth. This is called Solar eclipse. There is either a partial or total obstruction of the sun's light when viewed from the earth. A solar eclipse occurs on a new moon day when the moon is in line with the sun. However, due to the inclination of the moon's orbit, a solar eclipse does not occur on every new moon day.

ATMOSPHERE

The atmosphere is a gaseous en­velope that surrounds a celestial body. The terrestrial atmosphere, by nature of its composition, control of temperature and shielding effect against solar radiation, makes life possible on earth. It covers both the land and the water surface. It is bound to the earth by the gravitational pull of the earth. The composition of the atmosphere changes as we go higher from the earth's surface. Upto about a height of 50 km from the earth, the atmosphere is composed of: Nitrogen 78.09% Oxygen 20.95% Argon 0.93% Minor gases (Carbon dioxide, hydrogen, neon, helium, methane, xenon, krypton, etc.) 0.03% After a height of 50 km above the earth's surface the atmosphere is made up of atomic oxygen (O2), ozone (O3), helium and hydrogen. Atmospheric Layers These are the layers of air that lie above the earth's surface. The atmosphere of the earth is arranged into layers as accrued below, viz. Troposphere: The troposphere is the layer nearest to the earth's surface and extends from sea-level to a height of about 15 km. This region is the densest of all the atmospheric layers and contains water vapour, moisture and dust. In this region the temperature decreases as the height increases from the earth. Tropopause: Tropopause is the layer which separates the troposphere (lowest layer) from the stratosphere (upper layer). Stratosphere: This is the region of uniform temperature extending from an altitude of about 15km above the earth to a height of about 50 kill. It is free from water vapour, clouds and dust. Mesosphere: This is a very cold region and lies above the ozone-rich layer of the stratosphere. It extends from 50 or 80 km above the earth's surface. Menopause: The Menopause separates the mesosphere from the next layer called the ionosphere. Ionosphere: The ionosphere lies immediately above the mesosphere and extends from 60 to 400 km above the earth's surface. This layer contains ionised (or electrically charged) air which protects the earth from the falling meteorites (shooting stars) as most of them burn out in this region. It also protects the earth from the harmful radiations of the sun. The ionosphere consists of ‘D’, ‘E’ and ‘F’ layers and includes the thermosphere and exosphere. Thermosphere: This is the middle layer of the ionosphere. It is the region of the atmosphere where the temperature is above 100°C. Exosphere: The exosphere is the uppermost region of the ionosphere and makes up the outer limits of the atmosphere. Here the gravity of the earth is exceedingly weak. The magnetic belt of the earth which is known as Magnetosphere, extends to about 64,000 km above the earth's surface. The exosphere is now considered as part of the magnetosphere. The outer boundary of the magnetosphere or the final boundary between the earth and outer space is known its magnetopause. The land surface of the earth is made up of immense land masses divided into seven continents and a great number of islands. Together, they cover about one quarter of the earth's surface. It is believed that originally there was only one land mass called Pangaea. This large land mass split into a northern mass Laurasia and a southern one called Gondwana Land. From these two land masses, the continents gradually drifted to where they are now located and the process is still continuing.

Universe and Solar System

In the vastness of the Universe, the Earth, the Sun and planets are tiny dots. The Sun is a single star in a Galaxy comprising 100,000 million stars. The Solar System is centred on the Sun. It consists of a star called the Sun and all the objects that travel around it. The Solar System includes : 9 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto), along with the numerous satellites that travel around most of them; planet-like objects called asteroids (hundreds of asteroids); chunks of iron and stone called meteoroids; bodies of dust and foreign gases called comets (thousands of comets); and drifting particles called interplanetary dust and electrically charged gas called plasma that together make up the interplanetary medium. The whole solar system by volume appears to be an empty void. This vacuum of ‘space’ comprises the interplanetary medium. The speed of the solar wind is about 400 kilometer per second in the vicinity of Earths' orbit. The Solar System originated in a primitive solar nebula–a rotating disc of gas and dust. It is from this rotating disc that the planets and the rest of the Solar System evolved. The Solar System is also tucked away in a corner of the Milky Way at a distance of about 30,000 to 33,000 light years from the centre of the galaxy. The Sun contains 99.85% of all the matter in the Solar System. The planets which condensed out of the same disk of material that formed the Sun, contains only 0.135% of the mass of the Solar System. Jupiter contains more them twice the matter of all the other planets combined. Satellites of the planets, comets, asteroids, meteoroids, and the interplanetary medium constitute the remaining 0.015%.