Archives September 2013

"The ground was covered by some dark stuff that silenced all the wheels. ...It was like magic." Laura Ingalls Wilder, children's writer In the early nineteenth century, road maintenance was carried out by road gangs, who were often more interested in profit than in keeping roads in good condition. Scot John London McAdam (1756-1836) was a self-taught engineer, who had been appointed trustee of a turnpike. His neighbor suffered rickets and found traveling on potholed roads extremely painful, so McAdam began to experiment with different methods of road construction. Since the days of the Roman Empire, roads had been constructed with a bottom layer of heavy stone, topped by several layers of finer stone and a top layer of gravel. McAdam took this method, but used a compressed heavy roller to compact the layers of rocks together. McAdam's roads had graded layers of broken chippings, with a center higher than more...

A match consists of a wooden or paper stick with a coating of chemicals at one end that ignites when struck against an appropriate surface. The ignition results from thereat generated by friction as the two surfaces are rubbed together. The match enabled people to overcome the limitations of damp tinder and bad weather and create a flame at will, English chemist John Walker (1781-1859) created the first friction match in 1827. He owned a pharmacy in Stockton-on-Tees and manufactured an explosive chemical mixture for use in percussion caps, a component of firearms. He accidentally discovered that this mixture, made of equal quantities of antimony sulfide and potassium chlorate, ignited when rubbed along a rough surface. Walker had previously used chlorate matches, which ignited after being dipped in a bottle of sulfuric acid, but began manufacturing them using the new mixture instead. Walker called the matches "congreves." The chemical composition more...

In the olden times Jewish priests were very wicked. Their holy book said that people should hate their enemies. At that time a brilliant child was born in the family of a carpenter in the village Nazreth. His mother's name was Mary. When he was twelve year old his knowledge about God was more than the priests. At the age of twenty, he went in a jungle and kept fast for forty days and discovered the true path of life. He returned home and began to teach people that one should shed hatred and love their enemies. The most important lesson he taught to the people of the village was "Do to others only those things you would like them to do to you." He told the people that the world had grown wicked; But God is kind enough to forgive everyone who felt sorry for his mistake and confess more...

"The numbers [on the amplifier] all go to eleven.... Well, it's one louder, isn't it? It's not ten." This Is Spinal Tap (1984) A variable resistor—or rheostat—is a device that controls the flow of a current, rheo being Greek for "to flow." Rheostats are employed to adjust the current in electric machines, and to vary the resistance in electric circuits. Examples of their use are the dimming of lights and the controlling of a motor's speed. However, the way that most people encounter variable resistors is behind the knobs on radios or under the sliders on more complicated audio equipment. Turning the volume knob, you are moving the 'finger' of a variable resistor, changing the tapping point and therefore the' resistance, supplying more or less power to the speakers, which makes the sound louder or quieter. The variable resistor's design is based on the Wheatstone Bridge, which was invented by more...

The birthday of well known thinker and an eminent philosopher of the world Dr S. Radhakrishnan, 5th September, is celebrated as Teacher's Day. He was a teacher of great reputation before he became the President of India. So his birthday is celebrated as Teacher's Day throughout the country. As the teachers are the builders of nation they are given the rich tribute on this day.  Generally Teacher's Day is celebrated in a simple way. In certain institutions, teachers are relieved of their work of teaching and students of the senior classes attend the classes and teach the junior students. The Principal is also relieved of his burden today. The head boy of the school is officiating Principal on this day. Teachers pass their time in other activities. Some institutions celebrate this day with great pomp and show. Parent teachers association arranges the function to honour the teachers of their institution. more...

"Do you realize the sound only comes from one person? I've got a way to make it follow the person." Alan Blumlein, electrical engineer For most people, "stereophonic" means listening to audio through a two-channel loudspeaker system. Different elements of the recording can be heard to come from different directions, just as the human ear is naturally able to pinpoint the location of a sound. The man who invented stereophonic sound was an English electrical engineer named Alan Blumlein (1903-1942). While watching one of the early "talkies" in his local cinema in 1931, he became distracted by the disembodied effect of voices coming from a single location when the actors speaking were positioned across the cinema screen. The system he developed to enable the sound to "follow" the voice was called "binaural"—what we now know as stereo. His idea was a simple one. Two microphones were set apart by a more...

"The world has become uglier since it began to look into a mirror-everyday." Karl Kraus, journalist, poet, and playwright Primitive peoples would have found their reflections in the surface of still ponds, while mirrors used in early Greek and Roman civilizations and in Europe during the Middle Ages were highly polished pieces of metal that reflected light off their surfaces. However, the real leap forward for vanity occurred during the early sixteenth century, when the Venetians developed a method of backing a plate of flat glass with a thin layer of reflecting metal that was an amalgam of tin and mercury, much increasing the clarity of the reflection. The earliest mirrors were hand mirrors used for personal grooming, and later as objects of household decoration with frames made of ivory, silver, or carved wood. The chemical process of coating a glass surface with metallic silver, from which modern techniques of more...

“Archimedes has states that given the force, any given might be moved… Plutarch, Life Marcells The extent to which human beings extend their natural capabilities through the use of machines is something that distinguishes us from other members of the animal kingdom. Cranes are an especially relevant example of this; the ability to raise and maneuver weights vastly greater than those that people could lift and move unaided has played a defining role in the development of human society. The crane is a system of pulleys and cords or wires attached to a framework that enables the movement of heavy weights both vertically and horizontally through the use of mechanical advantage. The earliest cranes have been dated to approximately 550 B.C.E., although there are Greek architectural constructions still in existence that predate this by several hundred years, and that undoubtedly would have required some sort of supporting pulley mechanism. Cranes more...

"The use of radar in World War II... was a vital factor in the successful defense of Great Britain" R. Hanbury Brown, Robert Watson-Watt, physicists In 1935, with hostilities looming in Europe, the British government asked Scottish physicist Robert Watson- Watt (1892-1973) to develop a personnel-destroying "death ray" that could harm the opposition. Watson- Watt demonstrated that this was an impossible ambition. However, he theorized that a radio wave could be sent to bounce against a moving object, and monitoring its travel could then provide information about the target, such as its speed, direction of travel, and altitude. This could also determine the distance from the transmitter of fixed objects. A demonstration won favor with the government, and Watson-Watt subsequently gave the technology the name radar (radio detection and ranging). By the beginning of World War II, Watson-Watt had installed a chain of radar stations across the United Kingdom, and more...

Corruption is a deep-rooted menace that has eaten into the vitals of our society. There is hardly any sphere of social, economic, political and religious activity that is free from corruption of some kind. Corruption has become so common that most of the people have come to accept it as part of their life. Bribery and corruption has increased greatly after 1947. The growth of democracy and industry, the system of licenses and permits for setting up enterprises, securing quotas of law materials, imports and exports and expansion of trade and commerce is responsible for the increase in corruption. Stringent laws against corruption have proved to be effective in curbing this evil. Corruption flourishes as long as there are people who are prepared to give bribe and others who are prepared to accept it, directly or indirectly. Each one of us has a weakness for easy money. People are prepared more...