My Science School

          In the course of human evolution, at a certain point in time, the idea of living in a group with mutual under-standing and sharing became very useful and practical.

          From small isolated groups, communities were formed, and then societies, which in due course, became a civilization. But a civilization is much more than just a town; it is an advanced stage of organization.

          Civilization roughly means a highly developed social structure enriched by cultural, economic, and creative factors. It can include many things, like how different sections form in the society, how we interact with each other, how we create artistic works, how we dress, or how we govern ourselves.

          Most early civilizations flourished on riverbanks. This was because the river made the land fertile, and ensured the supply of water for agriculture. 

            While travelling in a plane, have you ever looked down and wondered why everything on the earth looked so small? The reason is that planes fly at great heights. The greater the height, the smaller will be the appearance of the objects on the earth. The height of the plane is measured by an instrument called the altimeter. 

            There are five main types of altimeters. The first is the pressure altimeter. It basically measures the decrease in air pressure as the altitude increases. The second is the radio altimeter. This is used to measure the time required by a radio pulse to travel from the airplane to the ground and back, much like radar. The third type is the sonic altimeter which makes use of sound waves. The fourth type measures the altitude by using the effect of atmospheric pressure on the boiling point of a liquid. The fifth type is the capacitance altimeter. 

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          Sanchi is famous for its stupas. This historic site is located to the west of Betwa River in Raisen district, Bhopal (Madhya Pradesh). It is about 90 m above its surroundings, and is the site of many famous Buddhist monuments. But how did the stupas come in to existence?

          Sanchi is the site of three stupas. Stupa No. 1, also called the Great Stupa, is one of the most magnificent monuments of its time. Its construction was probably started by the Emperor Ashoka in the mid-third century B.C. and later it was enlarged. It is enclosed by a massive stone railing pierced by four gateways. These gateways have elaborate carvings depicting the life of Buddha. Each gateway is made up of two square posts, topped by statues of animals and dwarfs. It consists of a base, bearing a hemispherical dome (anda) representing the dome of heaven enclosing the earth. It is surmounted by a square-rail unit (harmika) from which rises a mast (yatsi). It symbolizes the cosmic axis. The mast bears umbrellas (chhatras) that represent the various heavens (devaloka).

          Stupa No. 2, with railing decorations, has carvings relating to late Sunga period (1st century B.C.). Stupa No. 3, with its single gateway (torana), was constructed in the late first century A.D. These stupas have become an important site for tourist attraction. Thousands of people visit them every year.

          Certain other specimens of celebrated Indian sculpture are to be found at Sanchi. These include a commemorative pillar erected by Emperor Ashoka (265-238 B.C.) and the famous Gupta Temple built in the early 5th century.

 

          The custom of saluting has always existed in all cultures. A salute is a gesture of respect to a person of superior rank. 

          Until the 18th century, junior officers saluted by doffing their hats. In fact civilians still salute in this manner. This custom probably goes back to the middle ages when a knight would raise his helmet visor or uncover his head before a lord.

          After the 18th century, there came a change in the method of saluting, for a very practical reason! When soldiers fired their muskets, black powder used to settle on their hands, covering them with grime. And if they had to then take off their hats, it would spoil the hats! So by the end of the 18th century, the form was changed.

          In some cases it involved bowing and in others kneeling or laying on the ground or gesturing with hand and arm in a special manner. An officer or soldier carrying a sword at the shoulder salutes by bringing the hilt to his mouth and then the point to the right and downward. This form of salute goes back to the middle ages.

          The military salute of today — raising the right hand to the forehead or to the hat brim or visor is a recent innovation.  

          The word sextant comes from the Latin word “sextus” which means one-sixth. The sextant is an instrument used for measuring angles, primarily altitudes of celestial bodies like the sun or a star. It is also used in navigating ships and planes to determine the latitude. The height of the tall buildings and pillars can also be measured with the help of a sextant.

       Sextant was invented by an Englishman, John Hadley in 1731. The device consists of an arc of a circle, which is usually one-sixth of a circle or 60 degrees, and a movable radial arm pivoted at the centre. A movable mirror is fixed at the end of the arm. The other end extends to the scale. A telescope is mounted on the sextant, and a glass mirror is mounted in front of the telescope.

          To operate the sextant, the operator looks through the telescope straight at the horizon. Moving the mirror, the sun or any particular star is made to appear exactly on the horizon. The arm which moves the mirrors gives the required measurement of the angle. From this angle and the exact time of the day, the latitude is determined by means of published tables.

          The invention of sextant has laid the foundation of modern navigation.

          The land of the midnight sun is the popular name of the Scandinavian country of Norway, where from mid-May till the end of July, the sun doesn’t set completely. As a result, there is a long twilight, instead of night during this period. On its northernmost tip, the sun never sets completely for about two months in the summer, but at the same time there is no sun for two months in the winter.

          The midnight sun is seen in the Polar Regions when the sun appears above the horizon at midnight. Due to the tilt of the earth’s axis to the plane of its orbit by 23.5 degrees, each hemisphere is inclined towards the sun during the summer and away from it during winter. Due to this, the Arctic and Antarctic regions see the midnight sun for some time each year. When there is winter in the Antarctic region, day is indistinguishable from night. The sun does not rise and there is total darkness in the Antarctic Circle.

          At this time (April to July) the Arctic Circle enjoys summer with the sun visible for 24 hours a day. The sun rises in the sky and moves very slowly. Towards evening, it begins to set, until it reaches the horizon. Then it begins to climb again. At the Arctic Circle, this continues for about two months, but the actual midnight occurs on June 21.

          After six months, the Arctic region plunges into darkness and the Antarctic Circle is bathed in sunlight. Midnight Sun occurs in Antarctic from mid-November to the end of January.

          Extreme northern latitudes are sometimes called the ‘Lands of the Midnight Sun’. The Midnight Sun can also be seen near Bylot, an island of northern Canada. Every year thousands of tourists flock here to see one of the most impressive and extraordinary sights — the midnight sun. 

          The story of the discovery of the Ionosphere is very interesting. On December 12, 1901, G. Marconi demonstrated with his newly discovered wireless equipment that radio waves could travel across the Atlantic Ocean. This demonstration could not be explained with radio waves travelling in straight lines over the spherical shaped earth for such a long distance. So the scientists came to believe in the existence of some layer in the upper atmosphere, which acts like a mirror for radio waves and reflects them.

          In 1902, O Heaviside of England and A.E. Kennelly of the United States confirmed the existence of such a layer. This was called Heaviside-Kennelly layer. Watson Watt, the inventor of radar, coined the name ionosphere to this layer. Later in 1925, E.V. Appleton and M.A.F. Barnett of England experimentally proved the existence of the ionosphere.

          How did the ionosphere come into existence?

 

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            The parliament or the Central Legislature of India consists of the President and the two Houses: The Rajya Sabha (the Upper House) and The Lok Sabha (the Lower House).

            The President is an integral part of our parliamentary democracy, but it is still in many ways above the parliament. All bills passed by the parliament must have his assent before they become law. The parliament has to meet atleast twice a year and at an interval of not more than six months.

            The maximum strength of the Lok Sabha is 545 (525 from the States and 20 from the Union Territories), and of the Rajya Sabha 250 (12 nominated). 

            The Lok Sabha, whose life is five years after every general election, is the lower house of the parliament and comprises members directly elected by the people. Every citizen of India who is 18 years of age or above has been given the right to vote. To qualify as a candidate for election to the Lok Sabha, one must be a citizen of India and should not be less than 25 years of age. He should also possess qualifications prescribed by the parliament. The Lok Sabha elects two of its members as Speaker and Deputy Speaker for a term in consistent with the life of the Lok Sabha. The Speaker is the presiding officer of the Lok Sabha. He does not vote but can use his vote in case of a tie. He presides over the joint sitting of the Lok Sabha and the Rajya Sabha. The Speaker or the Deputy Speaker does not preside when a resolution for his removal is discussed in the House. The Lok Sabha can be dissolved before the stipulated or due time.

            The Rajya Sabha is the upper house of the parliament, and is made up of representatives from the states or the constituent units of the Indian Union. It is a permanent body, one-third of its members retiring every two years. Thus every member enjoys a six - year term. The Rajya Sabha cannot be dissolved since it is a permanent body. To qualify for election to the Rajya Sabha, the candidate should be a citizen of India, and not less than 30 years of age. He should possess such other qualifications as may be prescribed, under any law made by the parliament. The Vice-President is the ex-officio Chairman of the Rajya Sabha. The Deputy Chairman is elected from amongst the members of the Rajya Sabha.

            The Lok Sabha is more powerful than the Rajya Sabha. No bill can become a law, until it has been passed by it. The Lok Sabha shares with the Rajya Sabha the power of amending the constitution. It can also initiate a charge of impeachment against the President. The elected members of this house form a part of the Electoral College for the election of the President. The Vice-President is also elected by members of this house jointly with the members of the Rajya Sabha.

            No bill can become a law unless it has been passed by the Rajya Sabha. It shares the power with the Lok Sabha to amend the constitution. It can also introduce any bill except a money bill. No money bill can originate in the Rajya Sabha. All money bills passed by the Lok Sabha are sent to the Rajya Sabha for its recommendations. Such bills should be returned within 14 days, otherwise, they are deemed to have been passed. The members of the Rajya Sabha take part in the election of the President and the Vice-President. 

 

          The village of Khajuraho is in the Chattarpur district of Madhya Pradesh. This place was the capital of Chandela kings from 9th to 13th century. These kings built 85 temples between 950 A.D and 1050 A.D. Out of these only 20 temples survive today. These temples were dedicated to Siva, Vishnu, Brahma and the Tirthankaras.

          During this age India was called the Asian El Dorado. The people were prosperous and happy and the fertile land yielded plenty of crops, fruits and flowers. This climate was most conducive to creative efforts and temple-building emerged as its chief form.

          The Khajuraho temples are of the Indo-Aryan type. Each temple stands on a high platform and the customary enclosure is absent. The temples are in three groups and occupy an area of about eight square miles. The western group, the largest and most important, is situated at the axis of the Lalguan-Rajnagar road. The eastern group comprises Brahmin and Jain shrines close to the present Khajuraho village. The southern group is almost one mile away from the south of the village.

          The western group comprises the oldest Chaunsath Yogini, the Kendriya Mahadeva, the Devi Jagadambe, Chitragupta temple, Vishwanatha and Nandi temples. The other temples of this group are Parvati temple, Lakshmana temple, Matangesvara and Varah temples.

          The Eastern group consists of Vamana temple, Javari temple, Brahma temple, Adinatha temple, Parsvnatha temple and several other Jain temples.

          The Southern group has only two temples — Duladeo temple and Chaturbhuj temple.

          The temples of Khajuraho present a unique art and sculpture. They have engraved figures of gods and goddesses, celestial nymphs and hand-maidens (‘apsaras’ and ‘surasundaris’), bold serpents and leonine beasts and myriads of women. ‘Mithuna’ couples (rioting figures of love and lust) have accorded Khajuraho a distinctive status. At the centre of each temple there is the statue of an honoured god.

          In addition to these temples there is a small Archaeological Museum at Khajuraho, showing mainly sculptures collected on temple sites. The temples are visited by thousands of visitors every year. 

          After the World War II, an international body called the United Nations was set up to keep peace and prevent war, and to build a better world by dealing with problems which can only be solved through international cooperation. Today it has 184 member countries. 

          The Charter of United Nations was signed at San Francisco Conference on June 26, 1945 by representatives of 51 nations. The Charter came into force on October 24, 1945 when the governments of India, France, and the United Kingdom, the Soviet Union and the United States and a majority of other states had ratified it. The name, United Nations, was adopted at the suggestion of President Roosevelt of U.S.A. and the preamble to the Charter was largely the work of Field Marshal Smuts.

          According to the Charter the U.N. has four chief purposes. The first is to maintain peace by settling disputes peacefully or by taking steps to stop aggression (armed attack). The second is to develop friendly relations among nations, based on the equal rights of people and their own choices of government. The third is to achieve international co-operation in solving economic, social, cultural and humanitarian problems. And the fourth is to serve as a centre where the actions of nations can be combined to attain these aims. 

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            Do you know that about 3/4 of the earth’s surface is covered with water? There are three main oceans: The Atlantic, the Pacific and the Indian Ocean. The Arctic Ocean is taken to be a part of the Atlantic Ocean, and the Antarctic Ocean is made up of the southern parts of other oceans.

            The Atlantic Ocean is a great mass of water that separates Europe and Africa, from the American continent. It is shaped like an hour glass, with a ‘waist’ where Africa and South America bulge out towards each other. Although in area it is less than half of the Pacific Ocean, it has many ‘Secondary’ water bodies, such as the Arctic Ocean and the Mediterranean Sea.

            The Mediterranean Sea lies between Southern Europe, Africa and. South-West Asia. It is linked to the Atlantic Ocean through the narrow strait of Gibraltar in the west and to the Black sea in the north-east by the Sea of Marmara.

            One of the surprising facts about the Mediterranean Sea and the Atlantic Ocean is that while the water of the former appears blue, that of the latter appears green! Can you guess why this happens?

            The varying colours of the Mediterranean Sea and the Atlantic Ocean depend mainly on the amount of sunlight scattered from their surface. The colour of the scattered sunlight depends upon the substances dissolved in sea water. Generally, of the seven colours of the sunlight blue is scattered most. That is why most oceans appear blue. However, in the case of the Atlantic Ocean, the green effect is produced by the decaying plants in the ocean bed. When these plants decay, yellow pigments are released which get dissolved in the water. The water now scatters both blue and yellow light, and the resulting mixture produces the characteristic green shade.

 

          Man experiences weightlessness in a spacecraft. Anything that is not fixed or tied down just floats. Astronauts have to use special devices to eat and drink. The crew members have to learn to adjust the vigour of their actions to keep from crashing into the walls and equipments. During sleep also astronauts feel unstable and that is why they use belts during sleep. Let us understand more about this phenomenon. 

          The mass of a body is the amount of matter contained in it. In fact, it is the measure of inertia of the body. The weight of a body is the force with which the body is attracted towards the centre of the earth. Weightlessness occurs when there is no gravitational pull on the body such as in a spacecraft or when a satellite orbits the earth. If the force of gravity is balanced by the centrifugal force, the man in the spacecraft experiences a state of weightlessness. A body falling freely under gravity also experiences weightlessness.

          Sometimes, weightlessness causes nausea and giddiness because the working of the balancing organs in the inner ear gets upset. Particles floating in the spacecraft do not settle down easily and may be harmful for health. Astronauts are able to adapt to weightlessness through training.

         To make up for lack of gravity, regular exercise is essential in a spacecraft to keep the muscles in a good condition. It has been observed that in space, astronauts tend to ‘grow’ taller. This is because the pads of cartilage between the bones of the spine are no longer under pressure from gravity, and they expand. This increase in height can be as much as 5 cm. However, the astronaut returns to his original height when he returns to earth.

          Under the conditions of weightlessness it is possible to conduct certain scientific experiments that are impossible on earth. Absolutely perfect crystals can be grown and alloys of very high homogeneity can be made under the conditions of weightlessness which are very difficult to make under the pull of gravity.

          Scientists have been conducting experiments to find out whether a woman may become pregnant in weightlessness condition — and if so, what could be the effect of zero gravity on such children. In recent years, it has been discovered that prolonged periods of weightlessness can cause depletion of calcium in astronauts. 

          Ice Age was those early periods of the earth’s history when most of the northern part of the earth was covered by a vast sheet of ice.

          During the earth’s long history, there have been several ice ages. The earliest was in, what is called the late Pre-Cambrian times, some 700 million years ago. Another ice age occurred during the late Carboniferous and early Permian periods, about 280 million years ago. Finally about 2 million years ago, an ice age began which lasted nearly until our own times. This is known as the Pleistocene Ice Age. Here we shall discuss about the Pleistocene Ice Age only because information about the first two Ice Ages is not available.

          The Pleistocene Ice Age consisted of four periods. During each period, the ice formed and advanced southward, then melted back towards the North Pole. This happened four times. The ‘cold periods’ are called ‘glacial ages’ and the warm ones (when the ice melted) are known as ‘interglacial periods’. 

          The first period of ice came about two million years ago, and is known as Nebraskan. The second period came about 12,50,000 years ago and is called the Kansan. The third one came about 500,000 years ago. It is called the Illinoisan period. The fourth period, known as Wisconsin period, came about 100,000 years ago.

          In between these glacial periods, there have been three interglacial periods. These interglacial ages are called the Aftonian, the Yarmouth and the Sangamon Ages. A typical glacial age lasts about 40,000 to 60,000 years, and interglacial age lasts about 40,000 years. Ice of Wisconsin period began to melt about 40,000 years ago and ended some 10,000 years ago. According to geologists, the earth at present may be in an interglacial age.

          Geologists have learnt a lot about ice ages by studying fossils. Whole of Canada and one-third of northern United States, as far as New York City and the Missouri River valley, were covered by ice. In places the thickness of ice was from 2400 to 3000 m (8000 to 10,000 ft). In Europe ice covered whole of northern Europe, the British Isles and much of northern Russia. During the Pleistocene epoch, more than 30% of the earth’s surface was covered with ice.

          Plants and animals, too, were much affected by the advance and retreat of ice. A number of new animals such as camels, cattle and modern horses appeared during this Ice Age. Many lakes, such as the Great Lake of North America, were also formed during this period. 

            Plato was a great philosopher of ancient Greece whose writings and teachings still carry great importance. The works of this great thinker are read all over the world even now. He was a student of Socrates and teacher of Aristotle. In fact the ideas of Socrates were translated into writing by his great disciple Plato. He is also credited with implanting the seeds of Aristotle’s thought and intellect.

            Plato was born in 427 BC in Athens. He belonged to a wealthy aristocratic family and joined Socrates as his pupil at the age of 20. When Socrates was poisoned to death in 399 B.C. Plato left Athens in disgust and spent a few years in travelling. But he returned soon to establish his famous Academy in Athens in 388 B.C. which is considered as the first university in the world. 

     

    Plato’s teaching covered a wide range of subjects. But his views and thoughts on education, justice, and ideal state and ideal rulers are still hotly debated and discussed among the intellectuals. For him, ‘philosophy’ was the supreme thing and no learning is complete without it. He advocated the rule of philosophers, he said, “either Philosophers should be Kings or Kings should be Philosophers”. Justice for him was the performance of one’s duties. His model code for ideal rulers suggested that rulers should neither get married nor own property. He said that there is an ideal world beyond the real world which can be experienced only in one’s mind and man should always strive to bring the real world closer to the ideal one.

          There was another interesting aspect of Plato’s method of teaching. He didn’t permit his lectures at the Academy to be circulated in written form as he was afraid that readers outside the Academy might not understand his ideas correctly. His logic was that a man gets the opportunity to defend himself in a debate but cannot do so in his writings. So when he started writing his ideas he did so in the form of dialogues that provided the mention of different viewpoints along with his own.

          Among his books, the most famous is The Republic which is a political dialogue providing the requirements for an ideal state. This great philosopher died in Athens at the age of 80. 

            Generally while climbing up the stairs of a building, a person gets more easily exhausted, than while coming down. To lift heavy articles, greater effort is required. It is harder to walk uphill than downhill. Have you ever wondered why?

            We know that our earth attracts everything towards its centre. This is known as the force of gravity of the earth. It is the force of gravity that holds us on the surface of earth. When we move away from the earth’s surface, we have to do work to overcome the force of gravity. 

 

            So while going uphill, our muscles have to do more work to lift the weight of our body against the gravity of the earth. For this the heart has to pump more blood to the cells. As a result, our lungs have to do more work to pump out the carbon dioxide from the heart, and to replace it with oxygen. Hence for a steep climb we breathe more quickly.

            If we climb a mountain by two different paths — one more steep, and the other less — we would feel greater fatigue in the case of the steeper one.

            In comparison to the energy required for walking on a horizontal plane, the total value of the extra energy needed for climbing is the weight of the body multiplied by the total height to be climbed. 

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