Category Science

How can scientists control the weather?

            Since the 1940s scientists have discovered techniques by which. Several weather conditions can be controlled. For example, it is pos­sible’ to prevent lightning by using an electrical earth to diffuse the electrical content of a cloud. The American scientist V. J. Schaefer has shown .that it is feasible to produce greater concentrations of ice in clouds than occur under normal conditions.

            Weather experts already are taking advantage of these dis­coveries to increase snowfall on mountains for winter sports, to prevent damaging hailstones and to moderate, or even prevent, the development of dangerous storms. Scientists are now able, in some cases, to make a cloud burst to produce rainfall over parched areas.

            These local efforts may lead the way to large-scale weather con­trol. But before then scientists may’ have to learn to cope with the damaging effect of air pollu­tion on weather conditions.

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Why does India have monsoons?

     The seasonal winds of south-west Asia known as monsoons are associated particularly with India because of the lives of the inhabitants. The winds are drawn to India by changes in the temperature of the great land mass. A good monsoon season with plenty of rain means a comparatively good supply of food. A bad monsoon with little rain means a bad rice crop and, perhaps, starvation for many millions.

    Monsoons come from the Arabic mausim, meaning season. The summer season monsoon is a great inrush of moisture-laden air from the ocean. The winter monsoon blows from the land to the sea.

    In India there are three seasons: the hot dry season from March to June; the hot wet season from June to November; and the cool dry season from December to March. During the hot dry season the great plains of northern India becomes like a furnace and a region of low pressure develops.

   By mid-June, the pressure is low all the way to the Equator and draws the south-east trade winds to India, filled with water-vapour as they cross the Indian Ocean. When they meet the hot dry air over India, violent thunderstorms result, followed by steady rain in July. By November India has received three-quarters of its annual rainfall.

    Then the land mass cools and the lower pressure to the south attract the north east trade winds. These bring no rain to India except to the Coromandel Coast and Ceylon, where the rainfall in late September is heavy, because the winds have picked up water vapour as they cross the Bay of Bengal.

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Why does Holland have so many windmills?

          The large number of windmills in Holland, or The Netherlands, is due to the fact that they were needed to pump water into the canals off the rich, low-lying land reclaimed from the’ sea. Windmills are still used for this purpose today, but pump worked by electricity are more usual. 

          There is an Old Dutch saying, “God made the world, but the Dutch made Holland”. They certainly did make a great part of their land by dragging it from the sea, and the battle to hold it never ceases, The name Netherlands (from the Dutch Nederland) means low land, and more than one­ third of Holland’s land area of 12,530 square miles lies below sea level.

          Along the coast are dunes of sand-nature’s dykes-thrown up by normal tides. The Dutch plant them with marram grass, which holds the sand together with its long, strong, creeping roots. Behind the dunes the Dutch built three dykes of close-packed stone, clay and earth on wooden and concrete piles. The dyke nearest the sea is called a “waker’ Behind it lies a “dreamer” and behind that again a “sleeper” Some of the dykes are 200-300 feet high and many have a road or, some, a railway running along the top.

          In 1170 the North Sea swept into the country and formed the bay called the Zuyder Zee (South Sea). In 1421, another high tide flowed in to form the Holland’s Diep (Dutch Deep). The great spring tide of 1953 (two feet higher than any previously re­corded) smashed-the waker dykes, overflowed the dreamers and drowned about 1,900 people. About 50,000 were forced to flee from their homes.

          A famous Dutch story tells of a brave boy who stood for hours with his hand thrust into a hole in a dyke and so prevented the sea from rushing in and widening the breach in the wall.

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Who invented the parachute?

               Leonardo de Vinci (1452-1519) was thought until recently to have been the first to design a parachute. But drawings have now been found that were made five years before da Vinci’s sketches, possibly by an engineer in Siena central Italy.

               However, the first man to make and successfully use a parachute was a Frenchman, Andre Garnerin (1770-1825), who stretched cloth across a bamboo framework and parachuted from a balloon over Paris in 1797. It was an uncomfortable descent as the fabric was too thick o spill out any wind, and the parachute came down swinging violently like a pendulum. Garnerin was is a tiny basket, to which he clung tightly until his rough landing on the plain of Monceau. The parachutes of those days were developed from the crude canvas devices used to descend from hot air balloons.

               Modern parachutes are made of pure silk or good-quality nylon in small panels and have a small pilot parachutes which open first and helps to pull out the main parachute.

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When will a car engine stall?

             A car engine will stall-that is to say, it will suddenly stop when you do not want it to – if it is unable to provide sufficient power to overcome the load on the back wheels.

            This power is provided by the explosion of the petrol and air mixture pushing down on the pistons. If the load on the pistons from the crankshaft is exerting a greater force than that created by the explosion, the pistons will not move down the cylinder and the engine will stop. This can happen if the clutch is engaged too rapidly or if the hand brake is left on.

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What is fire?

           Fire is the outward sign that oxygen is combining with other substances in a spectacular chemical reaction. As the air is rich in oxygen, many materials will burn freely in a process scientifically called combustion, if their temperature is raised high enough. This explanation of what had been considered a mysterious phenomenon was discovered by the French chemist Antoine Lavoisier in 1783.

            The discovery of fire may have changed early man’s wandering mode of life to a more settled one because of an urge to keep the fire burning. It provided him with a new weapon for survival, warmed his cave and huts, enabled him to cook, and helped to scare off dangerous animals.

             In ancient time’s people in Persia, Egypt and India believed fire to be representative of the sun.

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