Category How does It works, How things work, How is it done, Curiosity

All computers work in basically the same way. They follow a set of instructions called a program that enables them to do calculations on information fed into them.

This process produces a result that is used in some way. The great advantage of computers over other machines is that the program can be changed, so that a computer can be given a wide variety of tasks to perform.

Computers consist of four main units – an input unit, a central processing unit is at the centre of operations and generally consists of a microchip located in the computer case. It controls the operations of all other units, which may be part of the computer or connected to it.

The input unit is used to feed information or data into the computer. It is usually a keyboard, but it may also be a light pen that interacts with a computer screen, or simpler devices such as a joystick, a mouse or a bar-code reader. The keyboard is also used to write programs.

The central processing unit first passes the information to the internal memory, where it is held temporarily. The program is also held in the memory, and the processing unit follows the program to produce the results. These go to the output unit, which is usually a video screen or printer, or they may be sent along telephone lines to other computers.

The computer also has an external memory unit such as disc drive that takes programs and data from the internal memory and records them for use at a later date.

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We have all at one time or another heard the echo of our own voice. An echo is caused by sound waves being bounced back from a solid obstacle, rather like a rubber ball bouncing off a wall. The same thing happens to radio waves which are sent out by a powerful transmitter. When the waves collide with a solid object they bounce back and can be picked up by a receiving set which is usually located at the same place as the transmitter. Since the speed of these waves is known we can tell how far away the obstacle is by calculating how long the waves take to cover the distance. This is how radar works.

The word ‘radar’ is an abbreviated form of the name ‘radio detection and ranging’. Radar is now used everywhere’ at airports, missile bases, space centers for following and tracking satellites and on ships and tracking satellites and on ships and aircraft for automatic navigation. A simple form of radar is used by police to detect speeding vehicles.

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You may have seen a certain type of lawn sprinkler which works by spinning round and round as the water squirts from it. The spinning movement is caused by the pressure of the water pushing against the movable arm of the sprinkler.

Sir Isaac Newton noticed something like this happening and it led him to discover an important law of nature. Newton’s law was that for every action in one direction there is an equal action in an opposite direction. In the case of the lawn sprinkler the water goes in and pushes in one direction and the sprinkler turns in the opposite direction.

The same law explains why a rifle recoils sharply when it is fired. The firing of the gun is known as the action and the recoil of the gun is the reaction.

The principle is what makes rockets speed through the air. Rockets are fuelled by very highly compressed gases. When these gases are violently released from the tail of the rocket the reaction they set up gives the rocket a mighty push in the direction opposite to the gas flow.

The greater the distance to be travelled, the greater must be the initial thrust. When Saturn V was launched, for example, its five engines consumed kerosene and liquid-oxygen at rate of 15 tons per second.

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It was far more difficult for man to discover how to produce artificial cold than it was for man to discover how to produce artificial cold than it was for him to produce warmth.

In olden days man tried to keep things cool during the summer by using snow or ice. This was a very difficult process. The snow and ice had to be carried down from the high mountain tops and stored in specially built places.

The ancient Romans, for example, brought their snow and ice from the Apennine Mountains. They dug large chambers in the ground which they called officinae reponendae nivis. This meant snow store. The store was covered in wooden boards and the ice was brought to the towns from the Apennine region near Rome and in Sicily from Mount Etna.

The first Experiments to produce ice artificially began in the seventeenth century. It was later discovered that in specified condition certain substances changed from a solid into liquid state. This fusion, or melting process, was found to be caused through the absorption of heat by those substances. As the heat was absorbed it was accompanied by a steady cooling of the temperature. Further experiments showed that the same absorption of heat could be carried out by evaporating and liquid. An example of this is when a sudden breeze evaporates the perspiration from our faces and makes us feel quite chilly. It is on this principle of heat absorption that ordinary household refrigerators work. The most commonly used liquid to bring about cooling is ammonia gas in solution. This solution runs through coiled tubes. It starts as a liquid and through compression becomes a gas which absorbs the surrounding warmth. This process is repeated over and over again until ice begins to form.

The first household refrigerator was made early in the nineteenth century. Since 1918 their use has becomes more and more widespread.

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In 1831 the Belgian physicist Joseph Plateau produced an apparatus which he called the phenakistoscope. This was followed by other devices such as the zoetrope or ‘wheel of life’ of the British inventor William Horner in 1834 and praxinoscope of the Frenchman Emile Reynaud in 1880. Despite their difficult names these apparatuses were all fairly simple and they all exploited a certain characteristic of the human eye.

If an object is placed before our eye its image is picked up by the retina, an extremely sensitive screen inside the eyeball. Every change of object outside causes a change in the image received by the retina and if the changes are rapid enough a whole line of images can blend into one. In the phenakistoscope and the other machines a series of image showing the various stages of a person in movements were shown on a revolving drum. All the images ran together and the viewer received the impression of continuous movement. Modern animated cartoons are also produced by rapid succession of drawings.

An important development in motion pictures took place in 1889 when the famous American inventor Thomas Edison, succeeded in using photographs instead of drawings. The photographs were taken one after the other on one roll of film. Edison then invented the Kinetoscope to show his moving pictures. This was kind of peep-show device which showed viewer about fifteen seconds of life-like movements.

The first truly modern cinematographic machine was produced in 1895. In that year the brothers Auguste and Louis Lumiere of France patented their famous and historic ‘cinematograph’.

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