When do we use a modem?



Computers that are connected to a telephone line incorporate a device called a modem. It turns signals into a form that can be transmitted along the telephone line. The name ‘modem’ comes from the term Modulator-Demodulator. The device modulates, or changes, the digital signal from a computer into an analogue signal, which is the type of signal that travels along telephone lines. The modem decodes, or demodulates, the signals it receives back so they can be read by the computer. Some modems are ‘voiceband’; that means they enable digital terminal equipment to communicate over telephone channels, which are designed around the narrow bandwidth requirements of the human voice.










Fact File



Robots are machines that ‘think’ with a computer brain which tells them what to do. A factory robot is often just a moving arm.




 



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When was the CN Tower built?



The CN Tower in Toronto, Canada is a communications and observation tower. This building was completed in 1976, and at that time was the world’s tallest free-standing structure.



The 20th century saw an explosion in communications technology. The first radio broadcast was made almost at the beginning of the century, when Reginald A. Fessenden transmitted music and words in 1906.



By the 1920s, radio provided a major form of entertainment for many people around the world. Then, in 1926, a Scottish engineer named John Baird developed the first successful television set.










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Communication satellites are used to carry communications such as radio, television and telephone messages around the world. These satellites are ‘parked’ in an orbit where they will remain in position over the same part of the Earth’s surface.




 



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When was the telescope invented?



Galileo is credited with having developed telescopes for astronomical observation in 1609. While the largest of his telescopes was only about 120 cm long and had an objective diameter of 5 cm, it was equipped with an eyepiece that provided an upright image. Galileo used his modest apparatus to explore the valleys and mountains of the Moon, the phases of Venus, and the four largest satellites, which had never been systematically observed before.



The reflecting telescope was developed in 1668 by Newton. He became the first person to use a telescope to see the moons orbiting the planet Jupiter. He also used his theories about gravity to show why the planets orbit the Sun.










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Special solar telescopes have been constructed so that the intensity of the image of the Sun or other planets, will not damage the observer’s eye.




 



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When was Braille invented?



The Braille system was invented in 1829 by a blind gentleman called Louis Braille. He developed a system which would allow blind people to read and write. It is today one of the most widely used alphabets for the blind.



The Braille system consists of dots. Each letter of the alphabet is represented by a combination of dots. These combinations are punched onto paper, so that they appear as raised bumps. A blind person reads the dots by moving their fingers over the bumps, recognizing each letter to spell out the words.



There were earlier systems of reading for the blind. Even as far back as 1517, alphabetic letters were engraved onto blocks of wood for the blind to read. This system was good to read by, but the drawback was that the blind could not see how to form the letters when they wanted to write.










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Semaphore is a means of communicating by using flags. Different flag positions represent different letters and numbers. It was widely used between ships sailing near each other in the days before radio.


 



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When was the first microscope used?



In the 16th century scientists were starting to look inwards at the secrets of the human body. They were able to use a new instrument to help them – two-lens microscope which had been invented in about 1590.



The Dutchman Antonie van Leeuwenhoek (1632-1723) started by using ground glass lenses to examine the world about him.



In the 1670s he made his first crude microscope with a tiny lens and this allowed him to be the first person to see microscopic life such as bacteria, yeast and living blood cells. During his career, van Leeuwenhoek ground a total of 419 lenses, and his microscopes became progressively more effective.



The English scientist Robert Hooke used an early microscope to discover the existence of living cells in plants.










Fact File



Some microscopes are so powerful they can magnify the smallest objects many thousands of times. This plant cell is invisible to the naked eye.




 



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When was atom structure discovered?



Niels Bohr was a Danish physicist. His mark on science and history was worldwide. His professional work and personal beliefs were part of the larger stories of the century. Bohr studied physics at the University of Copenhagen where he began to work on the problem of the atom’s structure. Ernest Rutherford had recently suggested the atom had a miniature, dense nucleus surrounded by a cloud of nearly weightless electrons. There were a few problems with the model, however. Bohr proposed adding to the model and this proved to be a huge leap forward in making theory fit the experimental evidence that other physicists had found over the years. A few inaccuracies remained to be ironed out by others over the next few years, but his essential idea was proved correct.



He received the Nobel Prize for this work in 1922, and it is what he is most famous for. Bohr was only 37 at the time and went on to make many other discoveries.










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Niels Bohr helped to develop the atomic bomb in 1943.




 



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When did Rutherford first split the atom?



Ernest Rutherford (1871-1937) was a physicist who studied radioactivity. He found several different forms of radiation and also discovered that elements change as a result of radioactive decay. He received the Nobel Prize for his work. Rutherford went on to discover the nucleus of the atom, and in 1919 he finally succeeded in splitting an atom for the first time.



He discovered the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like planets revolving around the Sun.










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Atoms become linked to other atoms by electrical bonds, which work rather like chemical hooks. Some atoms only carry one of these hooks while others may have many.




 



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When was gunpowder first used?



It was the Chinese again who first started using gunpowder in warfare. By the year 1232, the Chinese had discovered black powder (gunpowder) and had learned to use it to make explosive bombs as well as propelling forces for rockets. Drawings made in military documents later show powder rockets tied to arrows and spears.



When the Mongols laid siege to the city of K’ai-feng, the capital of Honan province, the Chinese defenders used weapons that were described as ‘arrows of flying fire’. In the same battle, it is reported, the defenders dropped from the walls of the city a kind of bomb described as ‘heaven-shaking thunder’.



In the same century rockets appeared in Europe. There is indication that their first use was by the Mongols in the Battle of Legnica in 1241. The Arabs are also reported to have used rockets in 1249.










Fact File



Guy Fawkes is best known for his efforts to blow up the Parliament building in England in England, in 1605. This became known as the ‘Gunpowder Plot’. His plan, however, was foiled and he was consequently arrested on 4 November, 1605.




 



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When were fireworks introduced?



Chinese crackers were probably the first fireworks to be made and this was about 2000 years ago. They are still used in China and throughout the East to celebrate weddings, births and religious festivals. They are also used to scare away evil spirits. It is probable that gunpowder was developed in China because they used potassium nitrate (saltpeter) to cure their meat, and so it was readily available.



Fireworks have also been used for centuries in ancient Indian and Siamese ceremonies.



The earliest recorded use of gunpowder in England is by the Franciscan monk Roger Bacon (born 1214). He recorded his experiments with a mixture which was very inadequate by today’s standards but was recognizable as gunpowder. His formula contained charcoal and sulphur because there was no natural source of saltpeter available.










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In January 1606 Parliament in England established November 5 as a day of public thanksgiving. The day, known as Guy Fawkes Day, is still celebrated with bonfires, fireworks, and the carrying of ‘guys’ through the streets.




 



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When was yeast first used in baking?



Thousands of years ago, the Egyptians discovered that it was the yeast which made bread rise and so they were the first people to produce a ‘yeast-raised’ bread.



Yeast is a one-celled plant, so small that it cannot be seen without a microscope. As yeast plants grow and reproduce, they form two substances called ‘enzymes’, invertase and zymase. These enzymes help to change starch to sugar and sugar to alcohol, carbon dioxide and energy.



This energy producing process is called ‘fermentation’. The carbon dioxide formed is a gas which man may use in a number of ways; one of which is baking, particularly bread.



Modern breadmakers add yeast and sugar to the dough as they make it. The starch and sugar in the bread dough serve as food for the yeast. Carbon dioxide is given off and forms bubbles inside the loaf. Heat from the oven causes the gas to expand. This makes the bread rise even more. Finally, the heat drives off the carbon dioxide, and it leaves a light, dry loaf.










Fact File



The first bread was made in Neolithic times, nearly 12,000 years ago, probably of coarsely crushed grain mixed with water, with the resulting dough probably laid on heated stones and baked by covering with hot ashes.




 



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When did the canning of food and drink first start?



People had been trying for thousands of years to find better ways to preserve food for a long time. The first patent for a ‘tin canister’ for preserving food was granted in England to Peter Durand in 1810. He got the idea from the canisters in which tea was packed. In America, the name became shortened to ‘tin can’, and the industry was called ‘canning’, while in England it is known as ‘tinning’.



The first cannery in the United States was one for fish, and was started by Ezra Dagget in New York City in 1819. Heinz & Company began producing baked beans in tomato sauce at Richmond, Victoria on October 1, 1935. To cam a food successfully, it must be heated enough to kill the organism (moulds, yeasts, bacteria) that may cause fresh food to spoil; the tin can or glass jar must be free from germs and it must be sealed air-tight.










Fact File



In 1810 the French chef called Nicholas Appert discovered a way of preserving food by packing food into wide-mouth bottles. He sealed the bottles and then lowered them into a boiler filled with hot water. A lid was put on, so that the bottles would heat in their boiling water bath. Some foods, fruit and vegetables in particular, may also be preserved by pickling then stored in jars.




 


When was the first electric lamp in use?



An American inventor, Thomas A. Edison invented the first workable electric lamp in 1879. In the late 1800s electric lamps began to replace gas ones.



On October 21, 1879, Edison created a lamp containing a carbonized thread for the filament. The lamp burned steadily for two days.



The first commercial installation of Edison’s lamp was made in May 1880 on the steamship Columbia. In 1881 a New York City factory was lit with Edison’s system, and the commercial success of the incandescent lamp was quickly established.










Fact File



In a modern electric light bulb, a current is passed through a very thin filament of metal that has a high resistance to the flow of electricity. The filament becomes white hot and produces light. The bulb contains an inert gas o the filament will not burn.




 



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When do we see the spectrum of light?



Sir Isaac Newton of Cambridge University in England, first uncovered the secrets of how light is divided up. We think of ordinary light as being ‘white’, but really light is a mixture of red, orange, yellow, green, blue and violet. When sunlight strikes the bevelled edge of a mirror, or the edge of a glass prism, or the surface of a soap bubble, we can see the different hues in the light. What actually happens is that the white light is broken up into the different wave lengths that are seen by our eyes. These wave lengths form a band of parallel stripes, each hue grading into the one next to it. This band is called a ‘spectrum’. In a spectrum the red line is always at one end and the blue violet lines at the other.










Fact File



Sir Isaac Newton used his discoveries about light to build a new kind of telescope. It used a reflecting mirror instead of glass lenses to magnify images.




 



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When was lightning first understood?



Ben Franklin (1706-1790) was an American with many talents. He was a printer, scientist and politician who played an important part in founding the United States.



He discovered the nature of lightning while flying a kite during a thunderstorm. Franklin noticed sparks jumping from a key tied to the end of the wet string. This could very easily have killed him, but it did not. He went on to invent the lightning conductor, a strip of copper that is run from the top of a building to the ground in order that lightning can earth itself safely.



Lightning is a significant weather hazard and occurs at an average rate of 50 to 100 discharges per second. Lightning rods and metallic conductors can be used to protect a structure by intercepting and diverting the lightning current into the ground as harmlessly as possible. When lightning is likely to occur, people are advised to stay indoors or in a car, away from open doors and windows and to avoid contact with any electrical appliances or plumbing that might be exposed to the outside environment.










Fact File



A lightning conductor is a metal rod that is placed so that it points upwards above the highest point of a tall building. If lightning does strike the building, it is the conductor, not the building itself, that the spark hits.




 



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When does lightning strike?



To understand exactly what lightning is, we must recall a fact we know about electricity. We know that things become electrically charged – either positively or negatively. A positive charge has a great attraction for a negative one. As the charges become greater, this attraction becomes stronger. A point is finally reached where the strain of being kept apart becomes too great for the charges. A discharge takes place to relieve the strain and make the two bodies electrically equal. This is exactly what happens in the case of lightning. This discharge follows the path which offers the least resistance. That is the reason why lightning often zigzags. Moist air is only a fair conductor of electricity which is why lightning often stops when it starts raining.










Fact File



The electrical nature of the nervous system was discovered after Italian scientist Galvani noticed how frogs’ legs twitched when an electrical current was applied to the nerve.




 



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