The first bicycle was just two wheels mounted on a rigid frame. It was built by French engineer J.N. Niepce and was the first ‘manpowered’ vehicle on wheels. Then in 1817, German nobleman Karl von Drais made a bicycle called the ‘Draisine’. This had handlebars and a front wheel that could be steered, so that the cyclist could change direction. Instead of pedals, the cyclist moved along by pushing with the tips of the feet. It had no brakes, which made it dangerous. In 1838 Scottish inventor Kirkpatrick Macmillan applied a system of gears to the wheels which were worked by the feet. But the modern bicycle was born in 1855, built by a young French workman, Ernest Michaux, who perfected Macmillan’s system by applying pedal directly on the front wheel. By 1860, the ‘michaudina’ had brakes. An important breakthrough came in 1896 when the first proper bicycle gears was patented by Englishman Edmund Hodgkinson . These enabled the cyclist to vary the numbers of spin...
In 1939, World War Two began in Europe. This war would last for almost five years. In Germany, Hans von Ohain designed and installed a completely new type of engine in an aircraft, an engine which would enable the aircraft to fly at a truly high speed. This was the first jet engine, pushed forward by air which was first sucked up and compressed, and the exhaust gases expelled at great pressure. Two years later, quite independently of von Ohain, an English engineer, Frank Whittle achieved the same results. But the first people to install the new motor in an aircraft were the Germans. Their Messerschmitt Me 262 , used during the last stages of the Second World War, gave the best performance. By the end of the War, jet engines had begun to be used in passenger aircraft, too. Now, people could fly at higher speeds and so complete their journeys within an unbelievably short time. Passengers tr...
HELLO GUYS, I will be explaining to you how we know what the stars are made of. Each Star Produces its own individual light. By splitting the light in a spectrum, astronomers can discover the chemical elements in the star’s atmosphere absorb light of different wavelengths. Sodium atoms, for example, only absorb light from the yellow part of the spectrum, called an absorption line, tells scientists that there is sodium in the star. By studying the various lines made on the spectrum, scientists can determine what the star is made up of.
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