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How Big is the Earth?

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The distance around the Earth, that is, it's circumference around the equator is 40,091 kilometres. The diameter (the distance across the centre of the Earth ) at the equator is 12,756 kilometres. The Earth is slightly smaller when measured between the poles (12,713 kilometres), so it is not an exact sphere. If the Earth is weighted on a weighing machine, it would be nearly 6x10 tonnes.
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When was Radar Invented?

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Radar was invented during 1930s. Many countries worked on radar at this time, but the first successful radar was built by Britain in 1935. Radar works by sending out radio signals that bounce off distant objects. The radar set detects the signals that return and produces a picture indicating the position of the objects . British and American scientists worked together to invent methods of using short waves called microwaves.
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When did Giant Mammals Live on the Earth?

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T he largest land mammal of all time was the giant hornless rhinoceros Indricotherium , which lived in the Oligocene epoch. It stood 5.5 metres high at the shoulder and its head would bypass a modern giraffe. Brontotheres stood at 2.5 metres at the shoulder. The horse like animal Moropus was a little smaller. All these animals browsed in the open plains.
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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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Who Feeds a Cuckoo?

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C uckoos are a family of parasitic birds. They do not build nests and lay their eggs in the nest of other birds. The female cuckoo keeps a watch on the nest of other birds while they build it and lay eggs. When the host parents are away, she flies down to the nest and pulls away one of the eggs with her beak. She then quickly lays her egg in its place and flies away. The poor host parents do not notice any change in the nest. After about two weeks, when the eggs hatch, the cuckoo chick pushes out of the nest. The foster parents keep on feeding the cuckoo chick which grows much larger than the foster parents. It stays with them until it is ready to fly .
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