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Monday, May 26, 2008

Why did Columbus sail westwards?

Christopher Columbus was an Italian from Genoa living in Portugal. Although in the fifteenth century most people still believed that the world was flat, others, including Columbus, had come to believe it was round. If this was so, he argued, a ship could sail around the globe and return to its original starting point. Thus the shortest route to the spice Islands of the East Indies would by sailing Westwards. He sought support for his theory but it was rejected again and again. Finally, after years of disappointment, he gained the help of Ferdinand and Isabella, the king and queen of Spain. In August 1492, three small ships set sail from Spain, their bows pointing westwards across the wide, unknown Atlantic. They were the Santa Maria, the Nina and the Pinta. On 12 October land was sighted. Columbus was convinced that it was an island off the coast of India. When other islands came into view he named them the ‘Indies’. His ‘mistake’ was nevertheless a vitally important event in the discovery and exploration of the west.


Friday, May 23, 2008

Why Australians are called “Diggers”?

Early in the 1800s, gold was discovered in Australia. Most of the ‘Strikes’ were in the vicinity of the Blue mountains near Bathurst. In 1851, a prospector named Hargraves – Who had been in California during the gold-rush two years earlier discovered rich traces of gold in Summer Hill Creek. The news spread rapidly and within two months the whole are was swarming with prospectors. The fact that there was gold to be had sent men digging in other areas, especially around Melbourne. In time the cities were deserted and ships lay empty in the harbours, for everyone seemed bitten by the lust for gold. Town sprang up overnight and were soon the scenes of rioting and bloodshed. The army has to be called in and a battle took place between soldiers and diggers. The incident became known as the battle of Eureka Stockade. By 1856, however, the day of the ‘amateur’ digger was almost over. Deep shafts had to be sunk to reach the gold and such mines had to be run by companies. But, in memory of the gold-flush days, Australians are still sometimes called “Diggers’.


Friday, May 16, 2008

What is a Cyclone?

Very simply, a cyclone is a kind of storm, and storm is air which is moving quickly from one Place to another.

A storm begins when a mass of warm, moist air from the equator meets a mass of cold, dry air from the northern hemisphere. The two masses of air will not mix- instead they form a front, which is just the name of the boundary where the two meet. The air in them continues to move, and the warm air rises above the colder air, becoming cooler as it does so. Then the moisture which was in the mass of warm air condenses and forms clouds.

Meanwhile, at the center of the storm, the air pressure begins to fall, and winds blow round this area of low pressure. In the northern hemisphere, the winds blow in the anti-clockwise direction, and this means that the warm air moves north round the eastern side of the storm, and the cold air moves south around the western side.

So a cyclone is just another word for a low pressure area. Such cyclones can be enormous, sometimes about a thousand miles in diameter.


Saturday, May 3, 2008

What is a Nebula?

One of the most stroking objects in the sky is the Great Nebula in the constellation of Orion. It can be seen as a faint greenish patch with the naked eye just below Orion’s Belt, but through binoculars or a telescope it is seen as a mass of glowing gas. Nebulae are large clouds of dust and gas in space. Many produce their own light, and others are illuminated by stars. Some are dark, and we see them as black clouds or bands against the stars. Many luminescent nebulae are formed when stars explode into supernovae. The remains of the star move out through space as an expanding shell of glowing gas. Nebulae are among the most striking sights in the heavens. Photographs show them to have beautiful colours, but these colours may not show in a telescope.


Thursday, May 1, 2008

What are Quasars?

The word quasar is short for quasi-stellar object, which means an object that resembles a star. But quasars are not like ordinary stars. Many are thought to be near the edge of the observable universe and moving away from us at nearly the speed of light. But quasars produce intense amounts of light and radio waves, and may be as much as 200 times as bright as an ordinary galaxy. And they appear to be much smaller than a galaxy-about one light-year across. No one can account for how quasars produce such immense amounts of energy. Perhaps they are much nearer, much larger, and not moving so fast.