Category Science

How was wheel invented?

          The invention of wheel has proved to be one of the biggest blessings for the mankind. It is used in almost all modes of transportation: trains, buses, trucks, cars, aeroplanes, scooters, cycles, rickshaws, bullock carts, etc. It has become very easy to cover long distances in a short time, thanks to the wheel.

          Before the invention of wheel, man himself carried the load. Later on, he started taming the animals like oxen, donkeys, horses and camels and used them for carrying their load. Gradually man started carrying load by dragging wood planks with the help of animals. Stone Age people may have learned to roll loads along on logs. The oldest known wheels looked like slices cut across a log with a hole in centre. Each solid disc was made of tree parts. After this invention, two wheels were joined by an axle and the axle was fastened to a platform of wood. This was the first crude cart of the world. In this cart both the wheels and the axle used to move.

          Later, a sophisticated version of wheel was developed. Wheels were made in ancient Mesopotamia (modern Iraq) between 3,500 BC to 3,000 BC. The picture of a cart wheel appears on some clay tablets from Mesopotamia dating 3,500 BC. About 2500 BC wheel was in use in Indus valley also.

         The next improvement in the use of wheel was fastening the axle to the vehicle and letting the wheels spin freely. The first wheeled vehicles were bullock carts, war- chariots and four-wheeled carts of the gods. Gradually the spoke wheel was invented in Asia about 2000 BC. This reduced the weight of the wheel considerably.

          With the passage of time, numerous improvements have been made in the design of wheels. Today, we have the rims and spokes of the wheels made of iron. Rubber tyres and tubes are put around them. To make tyres durable, nylon fabrics are used in rubber solution. Rubber tyres are so designed that these can have firm grips over the road surface to avoid skidding. Now wheel has become lighter, more efficient and long lasting. The invention of an unknown genius carried us a long way along the path of technology and civilization. 

 

How did Archimedes detect impurity in the golden crown?

          Archimedes, the “Father of experimental science”, was an ancient Greek physicist and mathematician. He was born at Syracuse in Sicily in the year 287 B.C. and educated in Alexandria. His teacher was a disciple of Euclid. The principles of science discovered by him are still taught to students. The famous “Archimedes’ Principle” tells us that if we weigh an object in air and then weigh it again when submerged in a liquid, it will apparently lose weight equal to the weight of the liquid it displaces.

          The story of discovery of the famous Archimedes’ Principle is very interesting. Once King Heron of Syracuse gave him a crown made of gold. He suspected that it was alloyed with silver. He asked Archimedes to test its purity without damaging it. It was absolutely a new problem for him. Interestingly he found its solution one day in a very peculiar manner. When he entered his bathtub, he found that his body displaced some water, and the water level in the tub rose. He then jumped out and ran down the street, naked, shouting “Eureka! Eureka!” (“I have found it! I have found it!”). He filled a vessel with water and dipped the crown in it. The water displaced by it was measured. Again he filled the vessel with water and dipped an equal mass of pure gold in it. The water displaced was again collected and measured. The amount of water displaced in the two observations was different. From this experiment he estimated the impurity in the gold crown. On the basis of this discovery he gave the method of finding out the relative density of different substances. 

          Archimedes also gave the laws of flotation of bodies and the principle of lever. He, for the first time, calculated the value of pi. In addition to these, he discovered the use of levers and pulleys and how to pump water uphill using Archimedean screw. The system is still used to irrigate fields in Egypt. He also designed war machines.

          Romans captured Syracuse in 212 B.C. At that time Archimedes had become quite old. One day while he was drawing some geometrical figure on the sand, one of the Roman soldiers asked him to accompany him. And when he refused, the soldier pulled out his sword and killed him. He was cremated with great honours. 

Why Newton is called the Father of Physics?

          Sir Isaac Newton is considered as one of the greatest scientists and mathematicians of all time. He was born on the Christmas morning of 1642 at Woolsthorpe in Lincolnshire. It was also the year in which the famous scientist Galileo died.

          At the age of twelve Newton was sent to school. When he was eighteen, he went to Trinity College at the Cambridge University. There he showed his brilliance in mathematics. In 1669 he became Professor of mathematics in the same college.

          Newton was very fond of making mechanical toys in his childhood. It is said that one day while sitting in a garden, he saw an apple falling to the ground. He began to wonder: “Why did the apple fall towards the ground? Why did not it go towards the sky?” Such questions puzzled him. He worked on this problem and finally gave his famous ‘Law of Universal Gravitation’. According to this law, everybody in this universe attracts every other body with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. He established the fact that the earth attracts all objects towards its centre. That is why anything thrown upwards falls back to the earth.

          Great scientist as he was, he solved many mysteries of the nature. He showed that the sunlight which appears white is in reality made up of seven colours. He could split these seven colours with the help of a prism. He also showed that the mixture of these seven colours produces white light. He also built the first reflecting telescope. His work on light and colour was published in 1704 in a book called Optics. He did monumental work in the field of mathematics. He gave the famous Laws of motion. He invented calculus. Newton’s discoveries were published in his book called Principia. It is one of the most important books of science ever published. On account of these researches Newton is called the ‘Father of Physics’.

          In 1689 Newton was elected as a member of parliament. In 1703 he was elected President of the Royal Society and was re-elected as president every year until his death. When he was 85 years old, he went to London to preside over a meeting of the Royal Society. But on his return he fell ill and he died on March 20, 1727.

 

Does any metal exist in a liquid state?

               Mercury is the only metal that exists in a liquid state. All other metals like iron, copper or aluminium are all solids. Mercury is also called ‘quick silver’. Although it is a liquid yet it possesses all the metallic properties. It is also a conductor of heat and electricity. It freezes at –39°C and boils at 359°C. It does not stick with the walls of the glass vessels. It shines like silver. It is 13.6 times heavier than water. All these unique properties make mercury very useful for us.

               Mercury is used in thermometers. It can measure temperatures from –39° to 359° Mercury is also used in barometers which measure the pressure of the atmosphere. Normal atmospheric pressure equals 760 mm of mercury. Although mercury is poisonous, yet it is used in the manufacture of several medicines and disinfectants. About one-third of the total production of mercury each year is used for medicinal purposes.

               In nature, mercury is usually found in a combined state. Its chief ore is cinnabar. It is a red ore and is obtained from many kinds of rocks. In olden days cinnabar was used for making red pigments. When the alchemists were trying to make gold by artificial methods, they invariably used mercury in their experiments. Today mercury is used in the manufacture of several paints, caustic soda, chlorine and electrical equipments. The vermilion that Indian ladies use is nothing but a compound of mercury. 

What is diamond?

          Diamond is the most precious and enduring substance in the world. It is the hardest material known so far. It cannot be cut by any metal or for that matter by any other thing except by another diamond only. Metal saw impregnated with diamond powder is used for cutting diamonds.

          Diamond which is a pure crystalline form of carbon is obtained from mines. At 900°C, it starts burning slowly and combines with atmospheric oxygen to form carbon dioxide. At 1000° C, it gets converted into graphite. At higher temperatures the rate of formation of graphite is faster.

          It is a good conductor of heat but a bad conductor of electricity. Its thermal conductivity is five times greater than that of copper. Diamonds vary in colour; they are either colourless or found in green, brown, white, yellow, pink and sometimes black.

          Until 1955, diamond was obtained only from mines but later certain synthetic methods for its manufacture were also developed. Diamond obtained from mines is called natural diamond, whereas the one made by synthetic methods is called artificial diamond. Africa is the biggest source of natural diamonds. About 80% of these come from this continent. Before they come to the market for sale, they are cut into different shapes and polished. The shine of diamonds remains intact even after hundreds of years.

          Synthetic diamonds were made for the first time in the world by the General Electric Co. of USA in 1955. In the synthetic process, diamonds are produced from graphite. In high temperature furnaces graphite is heated to about 3000° C under high pressure. By doing so graphite is converted into diamond. Synthetic diamond resembles the natural diamond in many respects. These are generally used in jewellery and industry. Industrial or inferior diamonds are also used for drilling and grinding. The weight of the diamond is measured in carats. One carat is equal to about 200 mg.

 

How is iron obtained from the earth?

          Iron is found everywhere on earth. It is not only present in the minerals but also in animals and plants. It is found even in the human body. Man began to use iron about 1200 B.C. after the Bronze Age.

          Five per cent of the earth’s crust is iron. It is estimated that the earth’s core contains huge quantities of iron and nickel. It is not found in a free state but occurs in a combined state with other elements. Its chief ores are: magnetite, haematite, limonite, siderite and iron pyrites. In India, these ores are mainly found in Bihar and Orissa. To obtain the iron from these ores, they are first finely ground with coal and limestone and then heated to a high temperature in a blast furnace. The melted iron comes out from the bottom of the furnace which, on cooling, becomes solid. The iron so obtained is called ‘pig iron’ and ‘cast iron’. It contains 5% of carbon. After reducing the percentage of carbon from 2 to 0.2% it is converted into steel. The process of the manufacture of steel from cast or pig iron is called “Bessemer Process”, named after Sir Henry Bessemer, who invented it in 1850.

          Iron and steel are very useful for us. They are used in all the industries in some form or the other. Appliances of our daily use such as knives, scissors, blades, locks, buckets, utensils are all made from iron. Ships, planes, trains, buses, cars, scooters etc. are also made from this useful metal. This is also used in the construction of bridges and buildings. Various kinds of nuts, bolts, pipes etc. are also made from iron.

          Stainless steel which is a very useful metal contains 18% chromium, 8% nickel apart from steel. In India, for making stainless steel, manganese is used instead of nickel because availability of nickel is rare in our country. Stainless steel has some special characteristics – chromium stops it from rusting and it is also not affected by acids and alkalies. Other steels are made with manganese, nickel and tungsten. Iron compounds are used to make pigments, inks and film for cameras. Iron oxide is used to make the tapes for tape recorders.