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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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Why does Mistletoe Grow on Trees?

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M istletoe is a plant which grows on branches of higher trees. It is a partial parasite since it has green leaves containing chlorophyll and can make its own food by photosynthesis. It takes the water and minerals it needs from the sapwood of the host tree. It is found growing on trees like apple, hawthorn, willow, poplar and lime . The seeds of mistletoe are spread by birds and once the seed germinates on the host tree, it develops haustorium . The haustorium is a tough structure and ensures of a regular supply of water and nutrients from the sapwood of the host to the mistletoe. The plant then develops a clamp like structure on the tree to be placed firmly.
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Why Must We Never Look at the Sun?

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The surface of the Sun is about four times hot as a furnace. The lenses or corner of our eyes act like a burning glass when we look straight at the Sun. The lens could be destroyed for life making us blind. Smoked glasses have been believed to be safe to look at the Sun. But even they are not safe. The Sun may look dimmer through it, but it cannot stop the harmful heat rays passing through it. Watching a solar eclipse with naked eye is very dangerous. To observe the Sun, we can project its image through binoculars or a telescope on to a sheet of white card. This can be viewed together by many people .
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Who is an Astronaut?

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An astronaut is a person trained to travel in space. Yuri Gagarin was the first person to orbit around the earth in 1961 and, since then, hundreds of them have been to the space. An astronaut should be extremely fit to survive the tremendous force of lift-off , which causes a feeling of the body being squashed. An astronaut is trained to operate spacecraft controls and to do other complicated works in difficult conditions. This could be performing experiments for scientists on ground, launching new satellites or rescuing damaged ones for repair. Once in the space, the astronaut experiences weightlessness. Eating and drinking present problems, since water breaks up into floating droplets and a haze of crumbs and debris would form. To avoid this, the food is squeezed into the mouth from sachets and liquid is sucked through a straw.
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What is Known About Mercury?

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Mercury is the innermost planet of our Solar System and has been once visited by a spacecraft , Mariner 10 in 1974. Photographs show Mercury to be atmosphere less and cratered, much like our Moon. Mercury's weak gravity cannot hold on to any gas to form an atmosphere. It rotates much slower than the Earth and takes two months to pass from sunrise to sunset. Being nearer to the Sun, it's day temperature reaches 4500C while the long nights are icy cold with the temperature of- 1700C. It is believed that a huge body must have crashed into Mercury several thousand million years ago causing a circular area 1,300 Km across, known as the Coloris Basin. Mercury has a very elliptical orbit around the Sun. It's distance from the Sun changes from 70 million Km when farthest away to only 46 million Km when nearest.
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