My Science School

           Since ancient times, man’s curiosity has led him to explore the dark, mysterious world of the deep seas. Diving has therefore developed to be an important sport over the years. But how do men stay under water for long periods of time?

          The first practical diving apparatus was devised by a German scientist, named Augustus Siebe in 1819. It comprised a metal helmet with a shoulder plate attached to a waterproof leather jacket. A tube running from the helmet was attached to an air pump. This was the first of many major experiments he carried out in trying to perfect a safe method of staying and working under-water. In 1830 he designed and developed a complete suit and helmet with air valves. Although many improvements have since been made, Siebe’s principles remain in universal use. 

          Deep sea divers, such as those who search shipwrecks for treasure, are divided into groups. They are skin divers who wear rubber suits that fit tightly like the skin, and divers known as ‘hard hats’ who wear heavy diving dress.

          A deep sea diver should use seven essentials: (a) An air pump for pushing air downwards to him. (b) A helmet, usually of steel, with glass windows to see. (c) A flexible waterproof suit fitting closely at wrists and ankles. (d) A length of air tubing that must be flexible, but must not collapse under the pressure of water. (e) A pair of heavy boots to keep the feet on the bottom. (f) Lead weights, hooked to chest and back, to prevent floating up to the surface. (g) A life-line to communicate with the surface by a system of jerks. One jerk may mean danger, and so on!

          Some divers also have a telephone so that they can talk to the ship. The wires for these telephones are built into the lifelines.

          Water pressure is a big problem for deep sea divers. The deeper a diver goes, more becomes the pressure of water around him. So the air pumped down must enable him to breathe properly and also balance the water pressure outside.

          In the past, deep sea divers used to breathe ordinary air, which contained nitrogen.

          This was very dangerous because when the pressure was very high, nitrogen would dissolve in the blood. When the diver surfaced, the pressure quickly returned to normal, which caused the nitrogen to bubble out of the blood. This led to a very painful illness which could even kill the diver, called as ‘Bends’ or ‘Caisson disease’. To avoid this, divers now breathe a mixture of oxygen and helium. Helium does not dissolve in the blood, so it is safer to use. But breathing helium makes divers speak with a high, squeaky voice because sound travels three times as fast as it does in air!

          In recent years, diving has not only become a popular sport, but is also useful in performing important jobs. Divers are needed for the construction and repair of bridges. They study plant and animal life beneath the surface of water. They aid in finding drowned people, and they also help in the search for buried treasure! 

 

          Sahara is the world’s largest desert covering an area of 9 million sq km. in northern Africa. It extends from the coast of Atlantic Ocean in the west to the Red sea and Iraq. It includes parts of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Sudan and Tunisia. One third of the desert is covered by sand dunes and the rest consists of rocky uplands and stony plains. Crude oil and natural gas have been discovered beneath the Sahara and now being extracted. But there was a time when this great desert was covered by ice. Do you know when?

          The first clue of ice was discovered when geologists found evidence of glaciations in the bedrock of the Algerian desert. The approximate time of the ice covering was calculated to be about 450 million years ago. The location of the desert at that time, as research studies have found out was near the South Pole. The size, shape and position of the continents or landmasses of the earth have been constantly changing over the years. This happens due to the movement of plates in the earth’s crust. When these giant plates move they carry the continents along with them. As per the available evidences, 200 million years ago there was a supercontinent called Pangaea. It was formed when separate continental plates drifted together but later Pangaea also broke apart. But geologists are not sure about the continental locations before the formation of Pangaea. But rock studies provide some clue to the then location of Sahara. They suggest that Sahara was situated near the South Pole which eventually leads us to believe that it was covered by ice during that period of history. This period, according to geological classifications, is called the Ordovician period when North Africa was at South Pole ice-cap and the equator ran diagonally across today’s North America.

 

            On a clear night, if we look up at the sky, we will see innumerable stars — small and big, bright and dim. Have you ever tried counting them? You’ll be surprised to find that out of these innumerable stars about 6000 can be seen without the help of a telescope!

            That does not mean that a person can just look up and count 6000 stars. From any one place on earth, only one-half are visible at one time as the rest of them are on the other side of it. Many of the stars near the horizon cannot be seen on account of haze. Hence if someone starts counting the stars, he would probably not be able to count more than 1000 of them. 

            By using a very powerful telescope we can see even very dim and distant stars. This way it would be possible to photograph more than 1,000,000,000 stars. Today astronomers have succeeded in identifying more than 4,57,000 stars.

            Now the question arises - why can’t we count more stars?

            Stars vary considerably in size, temperature, brightness and distance from the earth. We can count only those stars which are bigger in size, nearer to the earth, and bright enough to be seen by naked eyes. We can’t see the faint, smaller and distant stars without a telescope. However if we take a photograph from the same place by attaching a camera with the telescope, we can count more stars on the photograph, than we would with the naked eye. 

          Twentieth century astronomers have predicted dark areas in space. The gravitational attraction of these areas is so high that anything which goes into it cannot come out. Even light cannot escape their gravitational pull. Hence they do not emit light. These areas are called Black Holes or collapsars.

          A German astronomer, Karl Schwarzschild predicted the existence of black holes in 1907. He theoretically proved that black holes are the end results of all stars whose mass is much greater than that of the sun. The existence of black holes was first theoretically proved in 1939 by J. Robert Oppenheimer and Hartland S. Synder as a consequence of General Theory of Relativity. 

          Let us consider a star whose mass is greater than that of the sun. Its size remains normal due to the balance between the two forces — one being the expansion force caused by the enormously high temperature which tends to expand the star’s material, and the other being the enormous gravitational pull which tends to contract the star’s substance.

          At some stage in the star’s life, after thousands of millions of years, its nuclear fuel decreases causing a fall in its core temperature. As a result, the gravitational pull becomes stronger than the expansion force. Gradually the star begins to collapse.

          In this process, the atoms present in the star break into electrons, protons and neutrons. The mutual repulsion between the electrons prevents further contraction. The star, at this stage, is known as ‘White Dwarf’. In this process, the star is reduced to one-hundredth of its original size; thereby the gravitational pull in the White Dwarf becomes about 10,000 times more than the original value.

          Under certain conditions the gravitational pull becomes strong enough to overcome the electron repulsion. The star begins to contract further and in this process of contraction, electrons and protons combine to form neutrons. The star at this stage is called “Neutron Star”. Its size is now reduced to five hundredth part of the dwarf star and the gravitational attraction becomes about 100,000,000,00 times that of the original star.

          The light emitted from the neutron star reduces its energy and as a result its size further decreases. At some stage, no radiations come out from this star. It is then called a Black Hole which is the smallest and most dense object in the universe.

          Scientists are still looking for evidence of the actual existence of black holes in the universe. They have detected Cygnus X-1 as a black hole in 1974. In 1983, US astronomers detected another X-ray source in the large Magellanic cloud.  

           A satellite is a body that orbits around another but the term is usually applied to small bodies which orbit around the planets. Most of the planets have satellites revolving around them. For example, moon is the only satellite of earth. But apart from the natural satellites of the planets, several man-made or artificial satellites have been launched which now orbit the earth and some of the other planets in the solar system. But when did man send the first artificial satellite into the space? 

          The first artificial satellite was launched into the space by the former USSR on 4 October 1957 which was called Sputnik I. Sputnik is the Russian word for a travelling companion. It was spherical in shape with a diameter of 58 cms and weighed 83 kilograms. It orbited the earth every 96 minutes. A month later the launching of Sputnik 2, which weighed 500 kg, created another landmark in the space history as it carried the first ever space traveller, a dog named Laika. This established the fact that a warm-blooded animal could live in space thus paving the way for man’s venture into the space which finally succeeded in 1961 when Yuri Gagarin of USSR orbited the earth in his spacecraft Vostok I.

          The first American satellite was Explorer I which was launched on 31st January 1958 and weighed only 14 kilograms. The first American astronaut to be in space was John Glenn in 1962. The first woman space traveller was Valentina Tereshkova of USSR.

          But what functions do these artificial satellites perform in the space? They are used for radio and TV communications, weather forecasting, geological surveys, telecommunications, defence and spying purposes, scientific studies like space and astronomical observations, crop patterns and oceanography. Depending on their function they are called communication satellites, weather satellites, scientific satellites, earth resources satellites etc. Some satellites perform a number of functions and are called multipurpose satellites. 

          Empires rise and fall but the nation survives. India has survived as a great nation because unity in diversity has become an inherent feature of our country built over thousands of years. One of the most important pillars of this unity is the political unification, the present one being a gift of the British rules though the pre-independence British Empire was much larger. But long before the British Empire, India had witnessed great empires at different phases of its history; for example during the reigns of Ashoka, Samudragupta, Harshavardhana, Akbar, and Aurangzeb etc. But when did the first great Indian Empire arise?

          During the pre-Christian era some great civilizations had flourished in India but they had their geographical and political limitations. Thereafter arose some well-organized and better governed states but they were very small independent kingdoms. It was only after Alexander’s invasion that India saw the growth of its first ever large empire, under the adventurous leadership of Chandragupta Maurya. Initially Chandragupta was the Commander-in-Chief of the army of Nanda dynasty who were then ruling South Bihar in Eastern India. For some reason or other, Chandragupta attempted a revolt but was unsuccessful. He fled away and met Alexander the Great seeking his co-operation. When Alexander left India putting behind one of his generals in charge, Chandragupta again approached and got the help of this general. He became the ruler of Punjab and Bihar. A great political thinker of those times, Chanakya, also helped Chandragupta in his mission since he had also to settle scores with the Nanda dynasty. Thus the seeds of the first great Indian Empire were sown in around 321 B.C. and the rule of the great Maurya dynasty began. Later he extended his empire from the mouth of river Ganges in the east to the mountains of Hindukush between modern Pakistan and Afghanistan. This was the first really large and powerful centralized state in India.

          After empire building Chandragupta concentrated on defence and public administration. He maintained an elaborate spy network and an efficient bureaucracy. Though there was autocratic government at the top yet democracy prevailed at the village level.

          Later, Ashoka the Great became the third ruler of this great empire under whose reign the empire was further extended to the whole of India except the Deep South and south-east. The state progressed and flourished in all fields. 

          Our atmosphere contains about 78% of nitrogen. A certain amount of this nitrogen is constantly being removed, and an approximately equal amount is being returned. This continuous circulation of nitrogen among the soil, water, air and living organisms is known as the Nitrogen cycle. Let us see how the percentage of nitrogen in the air remains constant.

          All living things need nitrogen. It is part of proteins and nucleic acids, both of which are vital for life. How nitrogen is removed from atmosphere and again returned to the atmosphere is given below.

          A part of the atmospheric nitrogen is removed from the air by lightning. The sudden discharge of electricity causes some of the nitrogen and oxygen components in the air to combine, forming the oxides of nitrogen. When these nitrogen oxides are dissolved in water, they combine with other elements to form nitrogenous compounds.

          Some nitrogen is removed, from the air by certain bacteria and algae in a process called nitrogen fixation. Symbiotic bacteria present in the nodules of roots of some plants, such as peas, beans, gram etc. take up atmospheric nitrogen directly, and pass it on to the plants. Plants take up nitrogen compounds and convert them into proteins. These proteins are assimilated by animals. Some other plants, like rice, have symbiotic blue-green algae which fix atmospheric nitrogen.

          As a result of death, decay and excretion by plants and animals, the organic matter is converted into ammonium salts in the soil. Special nitrifying bacteria convert ammonia into nitrogenous compounds that are used up by plants. Animals get their nitrogenous compounds by eating plants, or other animals that eat plants.

          Thus an approximately equal amount of nitrogen is also being constantly returned to the atmosphere. Denitrifying bacteria change some of the nitrogenous compounds in the soil, back into gaseous form of nitrogen. These gases then return to the air.

          Thus nitrogen from the atmosphere passes into the soil, plants and animals and finally returns to the air. It may take thousands or millions of years, but every molecule of nitrogen eventually returns to the air.

 

          It appears strange but true that astronauts can walk in the space. This is so because in ordinary walking we rest our feet on the surface of the earth and the force of earth’s gravity pulls us towards it. But when there is nothing in the empty space – neither any surface to walk on nor any gravitational force to pull the feet down onto the ground – how does an astronaut walk in the space?

           Space walking by astronauts is quite different from the normal walking. To walk in the space the astronauts take the help of hand rockets which provide them the force to move. The hand rockets follow the principle of rocket propulsion. In rockets, the ejection of gas with a great force from the backside pushes the rocket forward with an equal thrust. This working principle is based on Newton’s third law of motion which states, ‘To every action there is always an equal and opposite reaction’. Similarly in hand rockets when the engine is powered the exhaust thrust pushes the rocket in the opposite direction and the astronaut walks along with this force as he carries the hand rocket with him. In fact, it is not ‘walking’ in the strict sense as there is no surface in the space to rest the feet but rather ‘floating’ – to express more accurately.

          But why do the astronauts walk in the space? Apart from experimental reasons, sometimes they are required to shift from one spacecraft to another or need to carry out a repairing work on the outer surface of the craft. During such operations they use the specially designed hand rockets and the direction of the exhaust outlet is pointed opposite to the desired direction of walking.

          The first spacewalk was made in March 1965 by a Soviet astronaut, A. Leonov, who stayed outside the aircraft for 24 minutes. Another important walk was made in 1973 when the American satellite Skylab was to be repaired for damage in the heat shield that made the craft dangerously hot. 

          The origin and development of any language can be traced back to the rudimentary symbols the primitive people used in their verbal interaction. These symbols when used over a long period take an established pattern thus giving rise to a new language. But the growth of a language does not stop at oral communication — a script for writing is developed on the way. But when did the first alphabet appear that enabled man to express himself in writing?

          The earliest people used pictures for writing which we call pictograph. The Stone Age people used this form in their writing. In pictograph a particular sign represents an object such as a tree or a bird which in turn communicates a specific meaning or idea. Ideas could be communicated through picture writing in the sense that the picture of a bird might mean flying. The ancient Egyptians also used picture-writing. But this form had its limitations. It required thousands of pictures, which were also called characters, to symbolize a few things. This drawback of pictograph led to the discovery of signs that represented sounds used in verbal communication. These signs representing different sounds were grouped differently to form new words. But when did the sound-signs first appeared which we now call alphabets?

          About 3,500 years ago, the Phoenicians in eastern Mediterranean, invented the first alphabet. Later the Greeks and Romans developed their own alphabets which were improvements of the Phoenician script. In fact the word ‘alphabet’ is derived from two words alpha () and beta () which were the first two letters in the Greek alphabet.    The appearance of alphabets made it easier to create thousands of words using a few alphabets. For example, there are only 26 letters in English alphabet but just imagine how many words we make out of these 26 letters! Pictograph lacked this advantage since one picture represented only one meaning or idea.

          Now most of the languages in the civilized world have their own alphabets but the number of letters in the alphabets and their pronunciation differ from language to language.

          If you visit the three pyramids of Giza, you will be surprised to see a colossal statue of a beast with a man’s head and a lion’s body! This is the great Sphinx that sits in the desert of Egypt, about 12 km from Cairo. The statue has mysterious eyes and enigmatic expression. It gazes over the desert with a kind of mystical superiority. It is one of the most famous monuments in the world.

          The Sphinx was carved out of the hill rock left over from the building of the Great Pyramid. It is about 20 m in height and 70 m in length. According to the popular belief, it was made some 5000 years ago to resemble the face of Chephren, a king of the fourth Egyptian dynasty. It was built during the reign of the Egyptian king Khafre.

            Now the question arises - why was the Sphinx built? The Sphinx was a mythical monster. The Greeks thought of it as having the head of a woman, and body of a lion with wings. The Egyptians thought of it as a wingless lion with the head and breast of a man. It was believed that the Sphinx would ward off all evils from the cemetery around the pyramids.

           Apart from the great Sphinx of Giza, there are many other Sphinxes in Egypt. Their heads represent different kings. In ancient Egypt, kings were considered to be descendants of the Sun God called Ra. When a king died, he himself was supposed to become the Sun God. Kings were also believed to have the strength of various beasts. So the Egyptians sculptured their Gods and Kings in the shape of half human and half beast.

           There is another Sphinx with a female face. It is made after the Queen Hatsphepsut, who had seized the throne and ruled the country. This Sphinx has a beard which represents queen Hatsphepsut’s masculine powers.

 

          Most people think that holes in woollen clothes are made by some species of moths. But this is not true. Moths do not eat wool. Then how is this damage caused?

          There are some larvae (caterpillars) of certain moths which feed on wool and other fabrics. The lifecycle of a moth is completed in four stages: egg, larvae, pupa and adult. The female may lay more than 1000 eggs on wool, furs, rugs etc. In about a week, the eggs hatch into caterpillars. Caterpillar is the name given to the larvae of butterflies, moths and sawflies. During this stage, the caterpillar’s main function is to eat and grow.

          Examples of different kinds of moths are: the case-making moth, the webbing moth and the tapestry moth. Caterpillars have mouths with strong, biting jaws that can chew cloth and fur. 

          The case-making caterpillar makes a little tubular case out of the wool it eats and lines it with silk. The caterpillar of the webbing moth always leaves a cobwebby trail of its silk and spins a silk cocoon. The tapestry caterpillar eats into the wool, makes a series of tunnels and lines them with silk. When fully grown, it goes into one of the tunnels and stays there until it is ready to come out as a moth. This is how caterpillars make holes in our clothes.

          Clothes can be protected against such damage by making sure that no eggs are laid by moth on the clothes. Before clothes are put away for the summer, they should be aired and brushed to ascertain that there are no eggs of moth on them. It is good to wrap clothes in heavy paper because moths cannot eat through paper. Moth balls keep the moths away, but do not kill the eggs or larvae which may already be present. The best way is to get the clothes dry cleaned before packing for the summer. 

          The Ajanta and Ellora caves attract many thousands of tourists every year. These caves are famous for their rock temples. The Ajanta caves are near Ajanta village, about 102 km north of Aurangabad (Maharashtra State). The Ellora caves are near Ellora village, about 29 km north-east of Aurangabad district.

          The nearest rail head for those visiting Ajanta is the town of Jalgaon, though Aurangabad is almost as close. There are also some provisions for accommodation around these caves.

          At Ajanta, there are about 30 caves. All of them have Buddhist rock cut cave temples and monasteries. The temples are hollowed out of granite cliffs on the inner side of a 22 m (70 ft) high ravine in the Wagurna River Valley. These caves were excavated between the 1st century B.C. and the 7th century A.D. They are of two types: ‘Chaityas’ (sanctuaries) and ‘Viharas’ (monasteries). In the larger caves, the pillars reach up to the roof. Most of the interior walls are painted and depict the episodes of Buddha’s life. The cave numbers 1, 2, 16, 17 and 19 possess some of the exquisite specimens of painting, while in the cave 1, 4, 17, 19, 24 and 26 one may find excellent sculptures.

          At Ellora, the caves extend along with face of the hill for about two kilometers and are divided into three distinct series – Buddhist, Brahmanical (Hindu) and Jain – and are arranged almost chronologically. Altogether there are almost 34 ‘Chaityas’ and ‘Viharas’ dating from the fourth to ninth centuries. The most splendid is the Kailashnath temple, 50 m (165 ft) long and 29 m (96 ft) high, cut from a single outcropping of rock. It is extensively carved with exceptionally vigorous sculptures of Hindu divinities and mythological figures. The temple dedicated to the Hindu God Shiva was built in the 8th century A.D. during the reign of the Rastrakutas. It has an open ‘mandapan’ in which colossal elephants and obelisks stand. It also has the sacred bull.

 

            When Napoleon was a mere boy, he used to identify himself with the great heroes of ancient history he read about. Today he is remembered as one of the few men in history who have been immensely powerful and exercised much influence on others. He was a benevolent dictator, i.e. he used his power for the good of the people and not simply to meet his own ends.

            Napoleon was born on August 15, 1769 in Ajaccio on the Island of Corsica. He was educated in France and when he was barely sixteen years old, he graduated from the military academy in Paris and became an army officer in 1785. When he was just twenty four years old, he fought during the French Revolution and was promoted to the rank of Brigadier General in 1793.

            The threat of revolt brought him the command of the army of the interior in 1795. He, then, commanded the army of Italy in several victorious campaigns. His expeditions to Egypt and Syria in 1798-99 were unsuccessful, and he was defeated by the British. However, he finally returned to France. A coup in 1799 brought him to supreme power as the First Consul and he instituted a military dictatorship.

            In the early 1800s, Napoleon made numerous reforms in the government and education. Under his rule industry expanded and universities flourished.

            He defeated the Austrians in 1800 went to war against Great Britain in 1803 and had himself crowned the emperor in 1804. His greatest victory, the battle of Austerlitz against Austria and Russia came in 1805. Thereafter, except for temporary setbacks in Spain, he was successful until his disastrous invasion of Russia in 1812. In 1812 he invaded Russia with an army of more than six hundred thousand men. Even though he captured Moscow, his army didn’t have enough supplies. So he had to retreat. Only about one hundred thousand men survived to march home.

            After several other defeats, Napoleon abdicated and was sent into exile on the Island of Elba. He escaped from Elba and returned to France. He gathered a new army and regained power for the period known as ‘the hundred days’. On July 15, 1815 he was defeated at Waterloo by the British commander the Duke of Wellington. Napoleon surrendered to the British, and was exiled to the remote Island of St. Helena in South Atlantic Ocean, 1200 miles off the African Coast. He was to spend the last six years of his life on this Island. He frequently quarrelled with Sir Hudson Lowe, the Governor, who had repeatedly prevented Napoleon from escaping. However Napoleon never gave up these attempts to escape. He also found time to write his memoirs.

            He died on May 5, 1821. It was rumoured that he had been poisoned, but modern historians and doctors refute this misconception. Now it is believed that he probably died of stomach cancer.

            Napoleon was a great soldier and a skilful diplomat, but he caused great sufferings to millions of people and ruined their lives.  

          Proteins are very important chemical compounds contained by all plants and animals. Probably life would not exist without proteins.

          The word ‘protein’ originated from a Greek word which means ‘first’, because proteins are considered to be the most essential part of the living matter. These chemical compounds are made up of chains of amino acids. There are more than 21 amino acids. Each amino acid has carbon, nitrogen, oxygen and hydrogen as its constituents. The different amino acids combine in different ways to form thousands of proteins.

            Proteins work in many different ways in the body. An important group of proteins, called enzymes act as catalysts in many biochemical reactions. Enzymes are essential for metabolic activity of the body. Some hormones, such as insulin, are also proteins. They are called regulatory proteins because they regulate blood pressure and blood glucose level. Immune proteins protect the body against infection. Transport proteins such as haemoglobin carry vital substances to different parts of the body. Movement of the muscles is helped by proteins called contractive proteins. Thus proteins are vital for the body. 

Continue reading "What are proteins? "

           Jalal-ud-Din Mohammed Akbar, the greatest of the Mughal Emperors of India, founded in 1582, a new religion called Din-i-Ilahi (or Divine Religion). This religion tried to bring together the Hindus and Muslims by combining the good points of Hinduism and Islam. Akbar wanted Hindus and Muslims to worship God at the same shrine in a common ritual. 

            Din-i-Ilahi was essentially an ethical system, prohibiting such sins as lust, sensuality, slander and pride and laying emphasis on virtues of piety, prudence, abstinence and kindness. The soul was encouraged to purify itself, through yearning for God, celibacy was condoned and the slaughter of animals was forbidden. There were no sacred scriptures or a priestly hierarchy in this newly-founded religion.

          But this religion did not attract many followers and practically died with Akbar. 

     Akbar (1542-1605) was the son of Humayun and the grandson of Babur. He was born on October 15, 1542 at Umarkot, Sind which is now in Pakistan. Akbar became the governor of Punjab at the age of 13, and succeeded his father, Humayun, to the Mughal throne in 1556. With able generalship, he overthrew his rivals and embarked upon a career of conquest, which by 1562 gave him domain over Punjab and Multan, the basin of the Ganges and Jamuna rivers, Gwalior to the south and Kabul in Afghanistan. Subsequently he crossed the Narmada River into the Deccan, and intended his dominion southward. By 1605 his empire contained 15 provinces or subahs and stretched from the Hindu Kush Mountains to the Godavari River and from Bengal to Gujarat.

           In order to preserve the unity of his empire, Akbar maintained good relations with the non-Muslim population. He won the loyalty of the Hindus as well as other communities also. He reformed and strengthened his central administration, centralized his financial system and reorganized tax collection procedure. Akbar was loved by everyone.