My Science School

 

 

 

The first talking movies were produced in France before 1900 by Leon Gaumont. They were short films, starring great performers such as Sarah Bernhardt, in which the moving pictures were synchronized with a gramophone record. By 1912 Eugene Lauste had discovered the basic method for recording sound on film, while Thomas Edison produced several one-reel talking pictures in the United States. An American, Lee de Forest, improved the system.

        In all this the public showed little interest until the presentation on October 6, 1927, of the Jazz Singer. This was a silent picture, starring Al Jolson, with four talking and singing interludes. Jolson’s electric personality and the very much improved sound began a movie revolution. Within the year every important picture was being produced as a “talkie”. By 1930 silent films were a thing of the past, and many film stars found themselves has-beens because their voices recorded badly.

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He lead in exhaust fumes comes from the petrol used to drive the internal-combustion engine. Crude oil straight from the wells is thick, black and sticky. It has to go through a complicated refining process before it can be used as fuel for the engines of cars, Lorries, buses and aircraft.

        During refining, various substances are added to improve the petrol and for other reasons. For instance, small quantities of dye are put in to standardize the colour. Other substances prevent the formation of gum which would clog up parts of the engine.

     Lead in a liquid from called tetra-ethyl lead, is added to petrol to reduce “engine knock”. This means that it prevents the petrol from igniting in the engine at the wrong moment. When an internal combustion engine is running, the petrol is lit by sparks from the sparking plugs. The petrol burns in what is really a series of small explosions and produces gases which come out through the exhaust pipe as dirty, smelly fumes. And the lead comes with them.

They are also encouraging car manufacturers to design internal combustion engines which will work efficiently on lead-free petrol and have cleaner exhaust fumes. These engines will be more expensive at first, but they will help to make the air cleaner and pleasanter where there is a lot of traffic.

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A star is a body of luminous gas, like the sun. But as stars are much farther away from the earth than the sun, they appear to be only small points of twinkling light. With the naked eye it is possible to see about 2,000 stars at any one time or place but with the most powerful telescope over 1,000 million stars are visible. Although light travels at 186,000 miles a second, the light from the stars takes many years to reach the earth.

     Stars are not fixed in space, but are travelling in different directions at different speeds.  Seen from the earth, these movements appear to be so small that groups of stars, or constellations, seem to have a permanent relationship. The star patterns we see in the sky are almost the same as those seen by our ancestors hundreds, or even thousands of years ago.

    The sizes of stars vary tremendously, from less than the diameter of the sun to thousands of times its size. Most stars appear white when looked at with the naked eye, but some are bluish-white, yellow, orange and red. The varied colours are due to differences in surface temperature. The brilliant, white stars are the hottest with surface temperatures of several hundred thousand degrees. The less brilliant, orange and res stars have surface temperatures of about 2,000 degrees.

      There are exceptions, however. Te red giant, betelgeux, in the constellation (or group) of Orion, appears to be brilliant because of its size. Its diameter is 250 million miles, which is greater than the diameter of the earth’s orbit round the sun.

     Shooting stars which are sometimes seen moving across the night sky for a few seconds are really meteors. These small particles flare up as they strike the earth’s atmosphere and usually burn out.

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Fertilizers are used on farms to increase crop yields by ensuring that soils contain the chemical elements required by growing plants. These chemical elements include oxygen, carbon, hydrogen, nitrogen, phosphorus, potassium, sulphur, calcium, magnesium, and iron. If soils are lacking in any of these, the deficiency can be made good by the right fertilizer.

     Until the 119th century, farmers relied mainly on the application of natural fertilizers put “goodness” back into the land. They used manure from the stock-yards and, in the case of coastal areas, seaweed from the shore. Lime was also applied to prevent acidity. This method of soil rejuvenation went a long way to maintain the presence of chemical elements. But it often did little to improve soils already lacking in certain chemicals.

      Nowadays soils are analyzed to find out deficiencies which can be made up by the application of the appropriate chemical fertilizers. Of course, the chemicals alone do not guarantee a successful crop. The continued application of the natural fertilizers, such as manure and humans (decayed vegetables matter) is also essential.

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An avalanche occurs when a mass of snow which has built up on a mountain side begins to slip and finally to fall. There can also be avalanches of earth, stones, rock and ice, but usually the word is used to describe a rapid fall of snow.

      Snow builds up to great thickness on steep slopes, especially if the surface is not smooth. Even a very small disturbance may set it in motion. The vibration of passing vehicle, the moment of a man or animal, the fall of a tree branch or even a sound can cause thousands of tons of snow to crash down a mountainside

    The speed of an avalanche varies enormously, but some have been estimated to move at about 200 miles an hour.  A big avalanche hurtles down the side of the mountain with a thousand roars, crushing or sweeping away anything in its path.

     The swiftly moving mass of snow pushes the air in front of it with such violence that it fans out sideways as well as driving directly ahead. This wind sometimes reaches a force almost equal to that of a tornado. This great wind is often a more powerful force of destruction than the avalanche itself.

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Alexander Graham Bell (1847-1922) invented and patented in 1876 the first telephone that was of any real practical use. In 1874 he said: “if I could make a current of electricity vary in intensity precisely as the air varies in density during the production of sound, I should be able to transmit speech telegraphically.” This is the principle of the telephone.

      On March 10, 1872, the first historic message was telephoned to Thomas A Watson, Bell’s assistant, who was in another room: “Mr. Watson, come here; I want you.”

     Bell’s first machine gave electrical currents too feeble to be of much use for the general public. In 1877 the American scientist Thomas A. Edison (1847-931) invented the variable-contact carbon transmitter, which greatly increased the power of the signals.

    The telephone was immediately popular in the United States, but Bell found little interest in Britain when he visited the country in 1878. Then Queen Victoria asked for a pair of telephone and the royal interest resulted in a London telephone exchange being formed in 1879 with eight subscribers.

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Cranes do not topple over because their jib or booms are counter-balanced at the opposite end from the lift load, thus keeping the centre of gravity over the base.

     The first cranes were simply long poles fixed in the ground at an angle, with a pulley at the top through which passed a rope. They were called “cranes” because they looked rather like the neck of the bird with the same name.

     The derrick crane, which looks like a gallows, is named after Dick Derrick, a 17th century hangman. In the middle of the 18th century, steam engines began to be used on cranes, while today the lifting may be done by varieties of power.

    Jib cranes may be portable being mounted on a portable being mounted on a wheeled carriage, or they may be self-propelled. Gantry cranes with long booms are used for unloading ships while overhead cranes are used in factories. Goliath cranes, with steel towers at either side, capable of lifting 200 tons are used at some atomic power stations.

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The first dish (or radio) telescope was made in 1942 by an American Grote Reber, of Wheaton, Illinois. He constructed his apparatus after studying the experiments of K.G. Jansky, another American. Jansky discovered in 1935 that the intensity of radio waves increases as a highly sensitive aerial is directed progressively nearer to the Milky Way. The maximum intensity is reached when the antenna is pointing towards Sagittarius that is to say, towards the galactic centre.

      Radio telescopes are called dish telescopes because of the steerable dish-shaped or parabolic reflector which gathers the radiation and focuses it on to a centrally mounted aerial. The surface of the dish is made of a good electrical conductor and the radio waves are reflected from it. The parabaloid shape ensures that all the reflected rays arrive at the central point, where they are “swallowed” by an electromagnetic horn and fed into a receiver.

    Since the Second World War the development of radio telescopes has gone ahead rapidly. A 250-foot diameter instrument was installed at the Nuffield Radio Astronomy Laboratories at Jodrell bank, Cheshire, England. It is under the direction of professor under the direction of Professor Sir Bernard Lovell and has already contributed a great deal of new information to astronomy.

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The Milky Way, or Galaxy, is the whole concourse of stars and other bodies which can be seen stretched across the heavens. It includes our own sun and its planets, as well as all stars visible to the naked eye. But the name is commonly restricted to the luminous band or belt where most classes of stars are concentrated.

       The spiral arms of the Milky Way are rich in hot, bright stars, interstellar clouds of gas (mainly hydrogen) and dust. The first evidence of spiral arms was obtained in 1951 by the American astronomer W.W. Morgan, who identified three.

     Our own system of sun and planets appears to be situated towards the inner edge of one of the arms, which is about 1,300 light-years away. The Andromeda nebula, a vast mixture of gaseous and solid matter, is visible as a small luminous patch in our sky. But it is comparable in size to the Milky Way and seems remarkably similar to our own galaxy.

    The Palomar telescope, 200 inches in diameter, situated on Mount Palomar in California, has perhaps 1,000 million galaxies within the scope of its vision.

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In the beginning our universe was a mass of white-hot vapours and molten materials whirling about in space. Our world was formed from this. Astronomers believe it took millions of years for the cloud to cool, contract and begin to turn into molten rock.

      Modern astronomers think that many millions of years ago there was a huge explosion in space. They do not know exactly what happened. But it is possible that our sun exploded or that a much bigger companion star of the sun became a supernova-that is, it broke up violently. The debris and blazing gases from this explosion were, it is thought, flung far into space.

      For more millions of years our solar system boiled and bubbled. But very slowly, the fiery redness began to cool and condense into the nine planets and many smaller bodies. All these planets now revolve around the sun.

     After further vast periods of time the lava of the earth began to solidify, developing over many millions of years, into the world as we know it today.

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Nobody knows for certain and, indeed, nobody has ever succeeded in proving that Prester John ever lived. The legend of Prester John or John the Priest-Prester is a shortened form of Presbyter-dates from the middle ages. According to these early legends Prester John was a mighty Christian potentate, a sort of King Priest of the Indies, of fabulous wealth and power.

       In the year 1165, the story goes, a letter was sent by Prester John, king of the Indies, to various European rulers, in which he claimed to be a “lord of lords” and hinted that he enjoyed a divine authority.

     The land of John was apparently an earthly paradise flowing with milk and honey. Justice and peace ruled supreme. Envy, flattery, greed, theft-none of these evils existed in John’s kingdom. Poverty, too, did not exist. So many people enjoyed high-sounding titles at John’s court, the letter claimed, that John himself used the plain title of Presbyter or Priest. Apparently John’s butler, in this fabled kingdom, was an archbishop and even his cook was a king.

     The idea behind this alleged letter to the European princes was that they should feel humbled that one as mighty as John should use such a modest title. Really the letter was an ingenious forgery and a satire on the princes of Europe.

      But the fable of a great Christian ruler lingered on. The crusaders loved the idea of this powerful Christian monarch ruling in the mysterious East. So the territories of Prester John were duly shown on medieval maps, although the boundaries were always vague.

     In later centuries it was suggested that the land of John really lay in Ethiopia, and gradually this became the accepted version of the legend. John Buchan makes use of the famous story in his adventure novel, Prester John.

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The night vision of Owls is 100 times as keen as that of human beings, because their eyes are especially adapted for seeing in the dark. But most are almost colorblind and the pictures they receive are slightly blurred. This is because their eyes contain more rod-shaped receptor cells than cone-shaped ones.

        Operating in bright light, cone cells sharpen details and react to colour. Rod cells gather light and owls have 10times as many of these as do human beings. Each cell contains “visual purple”, a substance capable of transforming the slightest glimmer of light into a sight impression.

   Owls have exceptionally large eyes and can control the amount of light entering by expanding or contracting the pupil. Each pupil can act independently of the other so that owls can see objects in the shadows and in bright light at the same time. Owls’ eyes are so large that they are supported by thin, bony, and tubular structures called sclerotic rings. Because of this the eyes are almost immovable and nature has compensated for this by giving owls extremely flexible necks, which enable them to turn their heads through an arc of 270 degrees.

     These birds have excellent binocular vision as their eyes are in the front of their heads. This gives them a tremendous advantage in swooping on small lively prey, because distance judgment depends on binocular vision. To add to their advantages at night, the owls have outstanding hearing, keener than that of any other carnivorous bird.

    But owls can also see well in the daytime. Although most species hunt by night, others are active at dusk or in full daylight.

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South America is largely Roman Catholic because the continent was first discovered and opened up by explorers from the strongly Roman Catholic countries of Spain and Portugal.

       Venezuela was the first of the South American countries to be colonized by the Spaniards. Christopher Columbus discovered it on his third voyage in 1498, and settlers soon followed in the early 16th century. Uruguay, discovered by the Spanish explorer, Juan Diaz de Solis, in 1515, was claimed over the years-until its independence in 1830-by both the Portuguese in Brazil and the Spanish in Argentina. Brazil, although first discovered by a Spaniard in 1500, was declared a possession of the Portuguese crown in the same year by Pedro Alvares Cabral.

       In the early 16th century, Colombia and Ecuador were also conquered by the Spanish. In 1532, Francisco Pizarro added to the Spanish dominions by the conquest of Peru and its Inca Empire, which at the time included much of what, is now Bolivia, Chile, Columbia and Ecuador

       Paraguay was claimed for Spain by Sebastian Cabot in 1526. The Spanish captain, Pedro de Mendoza, established a settlement on the site of what is now Buenos Aires in 1536. Although this was soon burnt down by Indians, Juan de Garay and other Spanish settlers reestablished the settlement in 1580 and gave it the name Santos Trinidada y Puerto de Santa Maria de Buenos Aires. This long name which means Holy Trinity and Harbour of Our Lady of kind Winds was soon shortened to Buenos Aires.

    This history of the Spanish and Portuguese control in South America is one of the oppression and exploitation. In the early 19th century, the colonies revolted and established republics. One of the strongest forces remaining from the centuries of colonial domination is the vital Roman Catholic faith of the conquistadores-the conquerors.

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The Great Fire of London began by accident in the house of King Charles II’S baker at pudding lane, near London Bridge, on September 2, 1666.

      Although it was the worst fire in London’s history, it performed a great service, for it cleansed the city after the Great Plague, which had rampaged through the country since 1664. During the Plague more than 75,000 Londoners died and many thousands more fled the city, leaving parts of it deserted.

      The fire raged for four days and burned the whole city except for the north-eastern and extreme western parts. The Royal Exchanges, St Paul’s Cathedral, nearly all civic buildings, 87 churches and about 13,000 houses were destroyed. Schemes were put forward for reconstruction, notably one by the great architect Sir Christopher Wren; but there was not enough money to replan the city entirely.

     However, many improvements were made, streets were widened, many houses were built of brick, markets were enlarged or recited, and Sir Christopher Wren’s genius created the beauty of a more splendid St Paul’s and 49 new churches.

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America and England were last at war with each other from June 1812 to December 1814. War broke out for two reasons: first, America’s expanding trade was threatened because the British were maintaining a blockade to prevent supplies reaching the French, with whom they were at war; secondly, there was a growing sense of nationalism in America, a feeling that she must fight to preserve her independence, sovereignty and honour.

      When war was declared by President Madison, the Americans immediately invaded Canada, but were driven back. In 1813, after talk of an armistice came to nothing, more skirmishes broke out on the Canadian border and British sailors began to raid the American coast. By October 1814 it became clear that the Americans could not successfully invade Canada, while the British Navy could do no more than harry the coasts of America.

    The chief sufferers were the merchants of New England. Also the financial state of the American government was so bad that it had no money to pay its bills abroad. Governor strong of Massachusetts openly spoke against the war, and was suspected of planning to take his state over to the British.

     However, no one in Britain wanted to fight the War of independence all over again. The desire was to trade with and not to fight against the United States. On December 24, 1814 the Treaty of Ghent was signed and the war was over. Neither side gained.

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