The Earth – Shape and Size
Shape of the Earth
Pythagoras (572-500 B.C.), a Greek philosopher and mathematician, was among the first to suggest that the Earth was shaped like a globe.
The Earth is not flat
1. If the Earth were a flat disc, then the rising Sun would have been seen at all places at the same time. But this does not happen. Places in the east see the rising Sun earlier.
2. When a ship approaches land, its funnel or mast is seen first and then the hull. If the Earth had been flat, the whole ship would have been seen at the same time.
The Earth is a sphere
1. The Earth is rarely oriented in the same position during successive eclipses but it always casts a circular shadow, thus proving that the Earth is a sphere. A sphere is the only solid body that will always cast a circular shadow.
2. At the North Pole, the Pole Star can always be observed at 90 degrees in the sky, since the star lies in the line with the axis of the Earth.
3. As one travels southwards, the angle of Pole Star decreases.
4. At the Equator the angle becomes zero degree.
5. This observation proves that the path of travel is an arc of a circle.
6. The Sun, Moon and all the heavenly bodies appear to be spherical when viewed from different positions. It seems logical to conclude that the Earth is no exception.
7. The photographs of the Earth taken from the space prove beyond any doubt that the Earth is a sphere.
The Earth as an Oblate Spheroid
1. Refined measurements of the Earth have proved that the true form of the Earth resembles a sphere that has been compressed at the poles and made to bulge at the Equator. This form is known as an oblate spheroid.
2. The various factors which make the earth suitable for
3. life to evolve and survive are
4. The earth has all the essential elements like carbon (in the form of C02), hydrogen (H2), nitrogen (N2) and oxygen (02) which act as building blocks for the origin of life.
5. The earth is neither too hot nor too cold. It has the right temperature range for carrying out the life-sustaining chemical reactions.
6. The earth has a lot of water in the form of lakes, rivers and oceans for the growth and survival of life.
7. The earth has enough oxygen gas in its atmosphere for the survival of living beings through breathing.
8. The earth has a protective blanket of ozone layer high up in its atmosphere to save life from harmful ultraviolet radiations coming from the sun.
Australia with New Zealand, Tasmania, New Guinea and the Pacific Islands (Micronesian, Melanesian and Polynesian Islands) is called Australasia by some geographers while some others call it “Oceania”, which includes proximate islands (Caribbean countries etc.).
Oceans on The Earth
There are four oceans. In order of their size, they are : Pacific Ocean, Atlantic Ocean, Indian Ocean and Arctic Ocean.
1. The explorer Ferdinand Magellan, who circumnavigated the Earth, named the ocean “Pacific” meaning calm or peaceful.
2. The Pacific Ocean (Area : 166,240,000 sq. km.) is the largest ocean of the world.
3. It is the deepest ocean with an average depth of 4,200 m.
4. The Mariana Trench is the world’s deepest trench with a depth of 11,033 metres (36,201 feet).
5. Most of the islands of this ocean are of volcanic or coral origin.
1. The Atlantic Ocean (Area : 86,560,000 sq. km.) is the second largest ocean in the world
2. Its name is derived from Atlas, a Titan (giant) in Greek mythology.
3. The Atlantic Ocean has the longest coastline.
4. The Atlantic Ocean is the busiest ocean for trade and commerce since its shipping routes connect the two most industrialized regions, namely Western Europe and N.E. United States of America.
5. The Atlantic Ocean was formed millions of years ago when a rift opened up in the Gondwanaland and the continents of South America and Africa separated. The separation continues even today and the Atlantic Ocean is still widening.
6. The continental islands of Newfoundland and British Isles are the major ones.
7. Volcanic islands are fewer and they include those of Cuba, Jamaica and Puerto Rico. Iceland is the largest island of volcanic origin.
1. The Indian Ocean (Area : 73,430,000 sq. km.) is the only ocean named after a country.
2. The Indian Ocean is deeper than the Atlantic Ocean.
3. It contains numerous continental islands, Madagascar and Sri Lanka are being the largest ones.
4. Some of the islands of volcanic origin are those of Mauritius, Andaman and Nicobar, Seychelles, Maldives and Lakshadweep are of coral origin.
South Indian Ocean
1. Warm currents : 1. South Equatorial 2. Mozambique 3. Madagascar 4. Agulhas.
2. Cool Currents : 1. Antarctic drift 2. West Australian currents.
1. The Arctic Ocean (Area : 13,230,000 sq. km.) is the smallest of all the oceans.
2. It lies within the Arctic Circle, hence the name Arctic Ocean.
3. The North Pole lies in the middle of the Arctic Ocean.
4. Most of the parts of Arctic Ocean remains frozen with thick ice for most of the days every year.
5. It is the shallowest of all oceans, with an average depth of 1,500 m.
6. It has the least salinity of all the oceans. It has a salinity of 20 unit per thousand.
1. The flow of a large amount of water in a definite direction with a great intensity is known as Ocean Current.
2. Ocean Currents are of two types-Hot and Cold.
1. The currents flowing from tropical zones of lower latitudes to higher temperate and sub polar zones are known as hot water currents.
1. The currents flowing from higher latitudes to lower latitudes are known as cold water currents.
2. The only exception to the conduction of ocean currents is found in the Indian Ocean. The flow of currents changes here with a change in the direction of the Monsoon Winds. The hot currents flow towards cooler oceans and the cold currents flow towards the warmer oceans.
Important Scientific Instruments and their usage
It is used to store electrical energy
It measures altitudes and is used in aircraft.
It measures the strength of electric current (in amperes).
It measures the force and velocity of the wind.
It measures the intensity of sound.
It is used for improving the imperfect sense of hearing.
It is used for continuous recording of atmospheric pressure.
It measures atmospheric pressure.
It is used to view distant objects
It measures heat radiation
It measures the quantity of heat.
It is used in an internal combustion engine for charging the air with petrol vapor.
It traces movements of the heart, recorded on a cardiograph.
It determines the longitude of a place in a ship.
It is an instrument used in cinema making to throw on screen and enlarged image of the photograph.
An instrument for comparing intensities of colour.
An instrument to change or remove the direction of an electric current, in dynamo used to convert alternating current into direct current.
It measures the growth in plants.
A charged particle accelerator which can accelerate charged particles to high energies.
It converts mechanical energy into electrical energy
It measures force, torque, and power
It detects the presence of an electric charge.
It examines the internal parts of the body.
A glass tube for measuring volume changes in chemical reactions between gases.
It measures the depth of the ocean.
It measures the electric current of low magnitude.
It measures the specific gravity of liquids.
It measures sound under water.
It measures humidity in the air.
It graphically records physiological movements (Blood pressure and heartbeat).
It determines the purity of milk.
It measures the pressure of gases.
It is an instrument used by the sailors to determine the direction.
It converts the sound waves into electrical vibrations and to magnify the sound.
It is used to obtain a magnified view of small objects.
An instrument by which the distance covered by wheeled vehicles is measured.
It is used to view objects above sea level (used in submarines)
An instrument for producing sound.
The instrument compares the luminous intensity of the source of light
It is used for comparing the electromotive force of cells.
It measures very high temperature.
A highly accurate clock used in astronomical observations and other precision work
Radio, angle, detection and range is used to detect the direction and range of an approaching aeroplane by means of radio micro waves
It measures the emission of radiant energy.
An apparatus for recording rainfall at a particular place.
An instrument used for the conversion of AC into DC.
It measures refractive index.
It measures the amount of sugar in the solution.
It determines salinity of solution.
It measures the intensity of earthquake shocks.
This is used by navigators to find the latitude of a place by measuring the elevation above the horizon of the sun or another star.
It is an instrument for measuring the energy distribution of a particular type of radiation.
An instrument used for spectrum analysis
It is an instrument placed in a vehicle to record its speed.
It measures the curvatures of surfaces.
It measures blood pressure.
It is used to view two dimensional pictures.
An instrument which is used by the doctors to hear and analyse heart and lung sounds.
It is used to view rapidly moving objects.
An instrument used in measuring speeds of aero planes and motor boats.
This instrument receives and sends typed messages from one place to another.
It views distant objects in space.
It measures horizontal and vertical angles.
This instrument is used for the measurement of temperatures.
It regulates the temperature at a particular point.
A small device which may be used to amplify currents and perform other functions usually performed by a thermionic valve
It is used to measure the amount of liquid precipitation over a set period of time. It is also called Rain Gauge.
An adjustable scale for measuring small subdivisions of scale
It measures the viscosity of liquids.
It measures the electric potential difference between two points.
The Constitution of India is the longest, written constitution in the world, with 464 articles under 25 parts, 12 schedules, 5 appendices, and 122 amendments today. The Constitution of India is the lengthiest constitution in the world as no other constitution contains as many articles.
India is a Sovereign, Socialist, Secular, Democratic and Republic State
The Constitution declares India to be a Sovereign, Socialist, Secular, Democratic, Republic.
➤Sovereign means absolutely independent, it is not under the control of any other state.
➤Socialist involves a system which will endeavour to avoid concentration of wealth in a few hands and will assure its equitable distribution. It also implies that India is against exploitation in all forms and believes in economic justice to all its citizens.
➤Secular means there is no state religion in India. Every citizen is free to follow and practice the religion of his/her own choice. The state cannot discriminate among its citizens on the basis of religion.
➤Democratic means that the power of the government is vested in the hands of the people, people exercise this power through their elected representatives who are responsible to them. All citizens enjoy equal political rights.
➤Republic means that the head of the state is not a hereditary monarch.
➤Federal Government: The constitution provides for a federal form of government. In a federation, there are two governments- at the central level and at the state level. The powers of the government are divided between the central government and the state government.
➤Fundamental Rights & Fundamental Duties: Fundamental Rights and Fundamental Duties are the most important characteristics of the Constitution. Fundamental Rights are considered to be essential for the proper moral and material uplift of people. These rights are fundamental in the sense that any law passed by the legislature in the country would be declared as null and void if it is derogatory to the rights guaranteed by the constitution.
➤Parliamentary Government: Indian Constitution provides a parliamentary form of government. President is the nominal head of the state. The government is run by the Prime Minister and other members of the Council of Minister. The Council of Ministers is collectively responsible to the Parliament.
➤Partly rigid and partly flexible: The Constitution of India is neither wholly rigid nor wholly flexible. It is partly rigid and partly flexible.
• Certain provisions of the constitution can be amended by a simple majority in the Parliament.
• Certain provisions can be amended by a two-thirds majority of the Parliament and its ratification by at least fifty percent of states.
• The remaining provisions can be amended by the Parliament by the two-thirds majority.
➤Single Citizenship: In the federation, normally we have double citizenship. In the U.S.A every citizen of the United States of America is also a citizen of the state in which he or she resides. But the constitution of India provides single citizenship to every Indian.
➤Independent Judiciary: The Indian Constitution provides for an independent judiciary. The judiciary has been made independent of the Executive as well as the Legislature. The judges give impartial justice
Disease caused by Viruses:
Chicken pox – It is caused by Varicella-zoster virus.
Small Pox – It is caused by Variola virus.
Common Cold -It is caused by Rhinovirus.
AIDS (Acquired Immunono Deficiency Syndrome) – It is caused by Human Immunodeficiency Virus (HIV).
Measles -It is caused by Measles virus.
Mumps -It is caused by Mumps virus.
Rabies – It is caused by Rabies virus (Rhabdoviridae family).
Dengue fever -It is caused by Dengue virus.
Viral encephalitis – It is an inflammation of the brain. It is caused by rabies virus, Herpes simplex, polio virus, measles virus, and JC virus.
Disease caused by Bacteria:
Whooping Cough – It is caused by a bacterium called Borde tella pertussis.
Diphtheria – It is caused by Coryne bacterium diphtheriae.
Cholera – It is caused by Vibrio cholerae.
Leprosy – It is caused by Mycobacterium leprae.
Pneumonia- It is caused by Streptococcus pneumoniae.
Tetanus – It is caused by Clostridium tetani.
Typhoid – It is caused by Salmonella typhi.
Tuberculosis – It is caused by Mycobacterium tuberculosis.
Plague – It is caused by Yersinia pestis.
Disease Caused by Protozoans:
Malaria It is spread by Anopheles mosquitoes. The Plasmodium parasite that causes malaria is neither a virus nor a bacteria
Amoebic dysentery: It is caused by Entamoebahistolytica.
Sleeping sickness: It is caused by Trypanosomabrucei.
Kala azar It is caused by Leishmaniadonovani.
Disease Caused by Worms
Tapeworm: They are intestinal parasites. It cannot live on its own. It survives within the intestine of an animal including human.
Filariasis: It is caused by thread.
Pinworm: It is caused by small, thin, white roundworm called Enterobiusvermicularis