A Scanner is an optical input device that uses light-sensing equipment to capture an image on paper or some other object . The image is translated into a digital signal that can be manipulated by optical character recognition (OCR ) software or graphics software . Scanners come in a number of types: Flatbed Scanner:: A scanner that provides a flat , glass surface to hold pages of paper, books and other objects for scanning is a flatbed scanner. The scan head is moved under the glass across the page. Sheet feeders are usually optionally available that allow multiple sheets to be fed automatically. Handheld Scanner: A handheld scanner can be moved across the image to be scanned by hand. Hand-held scanners are small and less expensive than their desktop counterparts, but rely on the dexterity of the user to move the unit across the paper. Trays are available that keep the scanner moving in a straight line .
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.
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.
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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