Category Science

Where the optical illusion of mirages occurs?

Sometimes when the thirsty traveler makes his way through the burning sands of the desert a lake suddenly appears before him just over on the horizon. The traveler then makes haste to reach this totally unexpected and welcome place welcome place of refreshment. Of course, the lake is not really there and what traveler sees is a mirage.

For a long time people thought mirages were hallucinations, an unreal vision like a dream that some people experience when they are ill. Then it was perfectly well, who were not hungry or thirsty. It was then learned that mirages are an optical illusion, a trick played by the air.

The temperature of the air we breathe differs according to the altitude. In the desert, air is warmer near the ground, which can extremely hot on summer days, and grows cooler as it rises upwards. Warm air is less dense than cool air and acts as a mirror or pool of water to reflect light. The reflections are often seen upside down as trees are in a still pool of water to reflect light. The reflections are often seen upside down as trees are in still pool of water. The warm, dense air also reflects the sky and the shimmering effect on the ground looks like a lake or pool.


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Who began flying?

Man has always longed to fly. In the late fifteenth century, Leonardo da Vinci was working on the problem of flying and a century later, a Jesuit priest from Brescia in northern Italy, suggested using the ascending force of the lightest gases present in the air. In 1782, the Neopolitan, Tibero Cavallo, filled a balloon with hydrogen and carried out some laboratory tests.

In France, a balloon full of hot air was publicly launched on 4 June 1783 at Annonay by the Montgolfier brothers, Etienne and Joseph. They repeated the experiment with a larger balloon at Versailles on 19 September 1783 when a hen, a sheep and a duck were the first living creatures to go up in a ‘Montgolfier balloon’. On 21 November the Marquis of Arlandes and Pilatre de Rozier, flew across from Paris, on board a hot air balloon.

The following month, December 1783, hydrogen was substituted for hot air. The physical J.H.C Charles with M.N Robert made the first manned flight using hydrogen.


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Where nuclear power is used to generate electricity in Europe?

An important world record in the field of nuclear science is held by Britain, where the world’s first atomic power station was built in 1956 at Calder Hall.

Since then, the generation of electric power by atomic or nuclear reactors has become increasingly important in Europe, where over 10 percent of total generating capacity is now nuclear. This is a higher proportion than in any other continent.

The leading European nuclear country in terms of nuclear power stations is France, which generates about a third of its electricity from nuclear fuels. Then come Germany, Britain, Sweden, Finland, Spain, Switzerland, Belgium, Bulgaria, Italy, Czechoslovakia, Yugoslavia and The Netherlands.

British nuclear power stations use a variety of different kinds of reactors, including an experimental fast breeder reactor at Dounreay. This is a kind of reactor that produces more fuel than it consumes and it could in theory generate immense amounts of power in the future.

However the technological problems involved have proved extremely difficult to solve and it is now doubtful whether the fast breeder will ever fulfil its early promise. Although nuclear power stations have to date worked well and safely throughout Europe, there is a mounting problem of radioactive waste disposal.                                                                                                                                                                                                          


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What do we know about hail formation?

Much of the hail that falls on Europe occurs in summer though scientists believe it is caused by cold temperatures. Some meteorologists believe hail is formed when a current of hot air rises to about 1,000 to 2,000 metres and collides with a cold air current that is descending. The sudden lowering of the temperature in the warm air current freezes the moist air it contains into the little pellets of ice that form hail. This process may be repeated several times, the hailstone gathering more and more coatings of ice, until it becomes heavy and falls.

Other meteorologists think that hail is produced by electrical processes.

Whatever the cause hail is a constant threat to farmers who for centuries have sought ways of defending their fields from it. Hailstorms do not usually affect large areas, but they can be so concentrated and intense that they destroy an entire year’s crop wherever they strike. Vineyards are frequently affected in this way.


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How clouds form in the sky?

The moisture in the air is the result of the evaporation of water by the heat of the Sun. The amount of evaporation depends on the quantity of water and the intensity of the Sun’s heat. Another fact that contributes to the increase of atmospheric moisture is the breathing of living creatures. All these factors combine to produce enormous quantities of water vapour which are continuously rising from the surface of the land and the sea and condensing in the atmosphere. When this happens the vapour turns into clouds of various types.

It was not until 1803 that clouds began to be classified scientifically. Luke Howard published a paper on clouds and the Latin terms which he used became the basis of the internationally accepted cloud classification. Further work was carried out towards the end of the century and the development of aviation stimulated further research. Clouds have been classified into three main groups by international agreement. The classification depends on the height of the clouds above sea-level. The groups are: cirrus, cirrocumulus, cirrostratus, between 2,000 and 7,000metres; stratocumulus, stratus, below 2,000 metres. There are clouds that build up like pillars from the land into sky to a height of over 6,000 metres. These include cumulus and comulonimbus.

When the condensation of water vapour in the atmosphere goes beyond a certain limit, it turns rain or snow.


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Where synthetic fibers were produced?

As far back as 1665 a British scientist predicted that artificial fibres would one day be produced. The first experiments were carried out about 200 years later by a Swiss scientist in Lausanne and the first industrial production of the fibre took place in 1884 under the Frenchman Chardon net.

Naturally it took some time for the fibres to become popular. In the first decades of the twentieth century rayon was being produced from cellulose. Protein fibres, made from such natural materials as casein, in skimmed milk, peanuts and soya beans, were also produced.

Today, the production of synthetic resins has made artificial fibres into a vast industry. Its products include nylon, dralon, orlon and Dacron which are used all over the world.


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Describe how sound travels through the air?

Everybody knows whether a sound is pleasant or unpleasant, loud or soft, mellow or sharp, but few people can actually explain what sound is and what are it qualities.

The string of a guitar or a harp is silent until it is plucked with the finger or a plectrum and set into vibration. The skin of a drum does not produce any sound until it is struck with a drumstick and made to vibrate. The sound of the saxophone is also produced by the vibration of its red. In a trumpet the noise comes from air that is thrust into the instruments and vibrated.

All sounds—the human voice, the noises made by animals, the tinkling of a bell or the buzzing of insects –is the result of vibration. Scientists have also discovered that there can be sound if there is no air to be vibrated.

An experiment was once carried out in which a bell was placed inside a glass jar. As soon as all the air was removed from the jar the ringing of the bell could no longer be heard.

Astronauts have confirmed that there is absolute silence in space.

It is easy, therefore, to see that sound spreads through the atmosphere like waves or ripples that spread outwards in a pond when something drops into it.


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In which the first signs of agriculture emerged?

The Fertile Crescent is a crescent-shaped region in the Middle East, spanning modern-day Iraq, Syria, Lebanon, Palestine, Israel, Jordan, and Egypt, together with the southeastern region of Turkey and the western fringes of Iran. Some authors also include Cyprus.

The region is one of the cradles of civilization because it is where settled farming first emerged as people started the process of clearance and modification of natural vegetation in order to grow newly domesticated plants as crops. Early human civilizations such as Sumer in Mesopotamia flourished as a result. Technological advances in the region include the development of agriculture and the use of irrigation, of writing, the wheel, and glass, most emerging first in Mesopotamia.

The main types of grain that were used for agriculture were wheat, barley, millet, and emmer. Rye and oats were not yet known for agricultural use. In Babylonia, Assyria, and the Hittite lands, barley was the main grain for human use: It was a widely used form of payment, and flat bread was made from barley. The smallest unit of weight was the equivalent of one grain (1/22 g). Beer and luxury foods were made from wheat and emmer.

Other agricultural products include sesame (derived from the Akkadian word šamaššammu), which was widely cultivated and used to make oil. Olive oil was produced in the mountains. Flax was used to make linen cloth. Peas were cultivated in Mesopotamia, while lentils were preferred in Palestine. Figs, pomegranate, apple, and pistachio groves were found throughout the Fertile Crescent. In villages and cities of southern Mesopotamia groves of date palms were common. The dates were eaten either fresh or dried, and palm wood was also used in crafts, but not in construction.


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In the study of the origins of agriculture, what does palynology mean?

Palynology is the study of pollen grains produced by seed plants (angiosperms and gymnosperms) and spores (pteridophytes, bryophytes, algae and fungi). Pollen and spores differ in their function, but both result from cell division involving a reduction by half of the chromosome content (meiosis) (Moore et al. 1991). Pollen grains house the male gametes, but spores are usually the resting or dispersal phase of the fern, algae, etc. Because of the larger size and the importance of pollen in pollination and to insects, pollen will be emphasized.

Pollen grains vary in shape from spherical to elliptic to triangular. Most pollen grains range from about 4 to 250 ìm. Pollen grains often have openings (pores) or furrows (colpus = singular, colpi = plural). A pollen grain with one colpus is called monocolpate. A pollen grain with three pores is triporate and one with three pores within three colpi is termed tricolporate. The outside layer of the pollen grain can be smooth (psilate), net-like (reticulate), or looks like a ball of string (striate). Some pollen grains even have spine like projections (echinate).

It is common knowledge that pollen is a major cause of allergies. However, pollen can be used to determine insect migration, insect food sources, honey types and in forensics, climatic changes, etc. There are several reasons pollen is used in these studies. First, pollen grains are distinctive, easily recognizable and identifiable to the family, genus and often species rank. Thus, very specific information can be obtained. Second, pollen is made up of sporopollenin that is durable and does not easily decay. Third, from the identification of the pollen, the geographical origin of the plant from which the pollen came can be determined.


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When did agriculture begin?

Taking root around 12,000 years ago, agriculture triggered such a change in society and the way in which people lived that its development has been dubbed the “Neolithic Revolution.” Traditional hunter-gatherer lifestyles, followed by humans since their evolution, were swept aside in favor of permanent settlements and a reliable food supply. Out of agriculture, cities and civilizations grew, and because crops and animals could now be farmed to meet demand, the global population rocketed — from some five million people 10,000 years ago, to more than seven billion today.

There was no single factor, or combination of factors, that led people to take up farming in different parts of the world. In the Near East, for example, it’s thought that climatic changes at the end of the last ice age brought seasonal conditions that favored annual plants like wild cereals. Elsewhere, such as in East Asia, increased pressure on natural food resources may have forced people to find homegrown solutions. But whatever the reasons for its independent origins, farming sowed the seeds for the modern age.

Cattle, goats, sheep and pigs all have their origins as farmed animals in the so-called Fertile Crescent, a region covering eastern Turkey, Iraq and southwestern Iran. This region kick-started the Neolithic Revolution. Dates for the domestication of these animals range from between 13,000 to 10,000 years ago.

Genetic studies show that goats and other livestock accompanied the westward spread of agriculture into Europe, helping to revolutionize Stone Age society. While the extent to which farmers themselves migrated west remains a subject of debate, the dramatic impact of dairy farming on Europeans is clearly stamped in their DNA. 


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