Friday, November 28, 2008
The earth behave as though there were gigantic magnet inside it. It has two "magnetic poles", which, at the moment, are about 1,000 km. away from the corresponding geographical poles. They are found in north east Canada and Antarctica, respectively. The magnetic poles are not stationary; they move in small circles over a period of about 500 years. The origin of the earth's magnetic field has not been completely explained. One theory assumes that because of the earth's rotation, the current molten material inside the planet act like gigantic dynamos, capable of producing the electric currents required to maintain the earth's magnetic field. Another suggests that the planet's heavy core is made of magnetic material.