Category Science

What are Auroras?

          An Aurora is a beautiful pattern of light that can sometimes be seen in the sky at night. The sky gets a glow with brilliant green, red, blue and yellow colours. An aurora near the North Pole is called Aurora Borealis, or the Northern lights. An aurora near the South Pole is called as Aurora Australis or the Southern lights. Sometimes both the phenomena are called “Aurora Polaris”.  But what exactly are auroras?

          Systematic scientific studies in this field began in 1716, when a spectacular aurora appeared in Europe and was visible in the entire continent. The English astronomer Edmund Halley proved a relation between auroras and the earth’s magnetic field. The most widely accepted theory about their origin is as follows.

          We know that our sun is a hot ball of fire. It produces heat due to fusion reactions. As a result, charged particles like protons, electrons, etc. constantly flow out of the sun. The flow of these charged particles is called solar wind. These particles travel through space in all directions at a speed of 480 km per second. As they enter the Earth’s atmosphere, they are attracted by the Earth’s magnetic field. The magnetic north and south poles change the direction and speed of these particles. These particles then collide with air molecules in the cold, thin upper atmosphere. This causes ionization, resulting in the production of coloured lights. These coloured lights are called Auroras. 

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What is immunity?

          Immunity is described as the ability of the body to resist or to recover from the invasion of disease-causing microbes (bacteria, viruses, and protozoas) and larger parasites (helminthes). Thus a person said to be immune to a particular disease would not contact it although others might do so.

          Microbes and parasites cause several diseases in man. The disease-causing germs often release toxins (poisonous substances). Normally our body is able to defend itself against most disease-causing microbes. First the skin acts as a barrier to the entry of many microbes. And secondly the white blood cells destroy many microbes. But if the number of microbes exceeds the capacity of white blood cells they fail to protect the body against them.

          Many persons are able to resist diseases to certain extent due to immunity mechanisms in their systems. The blood of a person produces substances called antibodies which fight the invading organisms. Each kind of antibody acts against only one type of microbe. Different antibodies have different characteristics. Some antibodies neutralize the toxins released by microbes. Certain others clump them together which can then be easily attacked by white blood cells. Some other antibodies dissolve the bacteria. Sometimes a certain amount of antibodies is permanently left in the blood plasma and this serves to protect the individual from future attacks. Such persons are said to be immune to that particular disease. 

          Immunological mechanisms are either specific or non-specific. Specific immunity, also called acquired immunity, which refers to mechanisms that are activated individually after a microbe or some other foreign material, invades the body. Non-specific immunity refers to general protective mechanisms that either kill or prevent the multiplication of microbes and other parasites.

          Some persons are immune to certain diseases right from the birth. These people are said to have natural immunity or inborn immunity. In an epidemic of a particular disease, say cholera, people with natural immunity do not suffer from cholera. If someone gets smallpox or chickenpox once, he will not get it again during his whole lifetime. The body in such a case retains adequate levels of antibodies as a protection against future infection.

          A person can also develop immunity by treatment with appropriate antigens. This is called artificial immunity. For instance, in the case of epidemics of smallpox, the health authorities vaccinate the people by which immunity is produced artificially. This vaccine was invented by Edward Jenner. It is produced by infecting a calf or horse with the smallpox virus. The virus in the calf or horse gets weakened. This weakened virus is collected as a vaccine and introduced into the human body. Since the virus is weak, it is not able to cause a severe attack of smallpox in man. But its presence induces the body, to produce antibodies and provides immunity against smallpox for several years. The introduction of weakened microbes in the body is called active immunity, the effect of which may last for even a lifetime. Immunity may also be passive. In this readymade antibodies are injected into the human body. An animal like a horse is infected with disease-producing microbes. The antibody is produced in the blood of the horse. The serum of the horse containing the antibody is extracted and introduced into the human body. The human body makes use of antibodies against the disease thus producing passive immunity. Passive immunity is produced almost instantly when the serum has been injected, but the effect lasts only for a short period.

          Vaccines are now produced to provide immunity against diseases like whooping cough, diphtheria, measles, tetanus, typhoid, polio, rabies tuberculosis, mumps, scarlet fever, German measles, and chickenpox. All infants should be provided immunity by vaccination for different diseases.

          In our country Haffkine Institute at Bombay and the Virus Institute at Poona produce several kinds of vaccines.

 

How do we see distant objects with binoculars?

        If you look through binoculars, you will find distant objects appear nearer and larger. Why does this happen?

        Binoculars are a pair of small telescopes built into a frame or casting. The two telescopes in binoculars are exactly similar in structure and meant for each eye. Each telescope is built into a funnel-shaped tube or cylinder. It consists of one objective lens and one eyepiece. The objective lens is kept towards the object and the eyepiece near the eye. The lenses are anti-reflection coated. Two prisms are also mounted between the objective lens and the eye piece to make the image of the object erect.

        The light from the object falls on the objective lens and an inverted image is produced by it. This image is further inverted by the two prisms, thus the image becomes erect. The eyepiece further magnifies this image. This is how we see the erect and magnified image of the object.

      

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What is the Theory of Relativity?

In the early nineteenth century people believed that light travelled through imaginary stationary medium called ether. It was believed that ether filled all space, and all movements could be measured absolutely with respect to it. It was also thought that the speed of light relative to a moving observer could be calculated in the same way as the relative speeds of any two moving objects. For example, just imagine two cars in the same direction: one going at a speed of 110 km/hr and the other at 80 km/hr. Passengers in the slower car would observe that the faster car is travelling at 30 km/hr.

Two American scientists, Michaelson and Morley, experimentally tried to measure the speed of earth through ether in 1887. But their result did not confirm the existence of the hypothetical medium ether. Later the explanation of negative results was offered by Albert Einstein. According to him, nothing like ether exists in the universe and the concept of absolute motion is meaningless. He also said that the speed of light is constant, no matter how fast the observer is moving. No material body can travel faster than light.

On the basis of his conclusions, Einstein formulated the Special Theory of Relativity in 1905. He showed that physical quantities like mass, length and time are also not absolute. They change as the bodies move. If a body moves with a large velocity, its mass increases and it becomes shorter. 

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How is nylon made?

            Nylon is one of the most important chemical discoveries of the 20th century. It is one of the toughest, strongest and most elastic substances we have today. It is a synthetic plastic material which is made from chemicals derived from coal, water, air, petroleum, agricultural by-products and natural gas.

            It was first developed by a research team headed by a U.S. chemist Wallace H. Carothers working in E.I. Dupant de Nemours & Co. He began experimenting with it in the 1920s. In 1935, he produced the first piece of nylon. It was converted into cloth in 1937.

            Nylon is made from two chemical compounds: Hexamethylenediamine and Adipic acid. Hexamethylenediamine consists of carbon, nitrogen and hydrogen. Adipic acid contains carbon, hydrogen and oxygen. Each of these substances contains six carbon atoms and the nylon produced by them has been named as Nylon-6, 6. Manufacturers combine the two compounds to form a substance called nylon salt. A solution of nylon salt is placed in an autoclave (a heating device). The autoclave heats the solution under pressure. Water is removed and the small molecules in the compound combine to form large molecules. This process is called polymerization.

            When caprolactam is used as the starting material, Nylon -6, 6 is obtained. It has been so named because it has six carbon atoms in the basic unit. It is comparatively a recent development.

            In some factories, the newly made nylon comes out of the machines as a plastic ribbon. This is then cooled, and cut into small pieces. Nylon fibres are made by forcing molten nylon through tiny holes in a device called spinneret. The thin streams of nylon that come out of the spinneret harden into filaments when they come in contact with air. Then they are wound into bobbins. From a single bobbin, as many as 2520 filaments are united into a textile nylon yarn. The fibres are drawn or stretched after they cool. The stretching action causes molecules in the fibre to fall into straight lines and make the fibres stronger and more elastic.

            Nylon can be formed into fibres, bristles, sheets, rods, tubes and coatings. It can also he rendered into powdered form for making moulds.

            Nylon fibres resist mildew and not harmed by most kinds of oil, grease and household cleaning fluids. It absorbs little water.

            Nylon is used to make many articles of clothing, parachutes, carpets, ropes, fishing lines and upholstery. It is also used in tyres and bristles in many types of brushes. Solid pieces of nylon are used to make bearings, gears and small machine parts. Unlike metal parts nylon bearings and machine parts need little lubrication.

            Recently a nylon derivative known as Qiana has been developed. It is a silk-like fibre used in clothing. Thus nylon has proved to be useful in many ways.  

How does a crane work?

          You must have seen a crane lifting and moving heavy loads at construction sites and other places. The machine got its name from its resemblance to the crane bird which has a long neck!

          Although cranes have been in use .since ancient times, their widespread use only began in the 19th century with the development of steam engines, internal combustion engines and electric motors.

        Basically, cranes are of two types: fixed and mobile. The mobile cranes are more common. Some have a jib or boom that can move up and down and can swing around in a circle. Some others form a bridge and can lift a load up and down, move it along a track and move it from side to side above the construction site. 

          A common mobile crane is the crawler. It is mounted on a vehicle with wheels. These cranes are mainly used for civil engineering and construction work. They can lift heavy loads upto around 72 tons and can have a boom length of 30 m (100 ft) or more.

          Another type of crane is the hammer head or cantilever crane. It is used in the construction and erection of tall buildings. It has a long horizontal jib that is cantilevered and mounted on a tower. The tower can be raised by jacking it up, floor by floor, as the building becomes taller. The load is suspended from a trolley that moves along the jib. 

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