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When were the First Mechanical Clocks Made?

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The first mechanical clocks are believed to have been made in China in 1088 AD. Later in 1200s, they were first made in Europe. Such clocks made in Europe were driven by a weight on the end of a cord wound round a drum. As the drum rotated, it turned the hands of the clock. The earliest known clock was made in Spain in 1276 AD and the oldest mechanical clock that still works is in Salisbury cathedral in Britain. It was made in 1368. These clocks had devices called escapements to keep the hands turning at the correct rate, so that the clocks depicted the correct time.
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Where are Diamonds Found?

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Diamonds are crystals and are the hardest naturally occurring substance in the world. They are formed by intense heat and pressure, deep beneath the surface of the Earth. They are made up of pure carbon and are usually colourless. Diamonds have to be cut in a special way to catch the light and sparkle. Diamonds have been formed millions of years ago from carbon which was caught up in molten rock deep in the Earth's crust. South Africa, Tanzania and Siberia have been mined for diamonds. Diamonds also come from the gravels of rivers in some areas in Africa , India, Indonesia, Brazil, Australia and Russia . 
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What is a Geostationary Orbit?

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Artificial satellites sent from the Earth orbit around the earth. The ones near the Earth orbit faster than the ones far away. A satellite 35,900 Km above the Earth's surface, takes 24 hours to orbit once. The satellite is always above the same point on the Earth's surface as the planet rotates. Geostationary orbit is also called as geosynchronous ' orbit. Such satellites are used to receive telephone and television signals and retransmit them over long distances.
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