Monday, May 26, 2008
Friday, May 23, 2008
Early in the 1800s, gold was discovered in
Friday, May 16, 2008
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
Thursday, May 1, 2008
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.