英语听力：自然百科 地球力场 Earth's Force Field—18（在线收听） |
Earth's magnetic field has reversed thousands of times since its formation 4.5 billion years ago. And scientists now believe that the next reversal is imminent. The race is on to predicting exactly when it will occur. In 2010, the European Space Agency will launch SWARM. Its mission is to generate accurate, up-to-the-minute maps of the Earth's magnetosphere and anticipate its future activity. Professor Nils Olsen of the Danish National Space Center is working on the mission. “Then you’ve had exciting idea behind SWARM is that we have three satellites. We have higher satellite at an altitude of 530 kilometers and we have a pair of satellites at an altitude of about 400 kilometers.”
These identical satellites are equipped with new generation magnetometers. These will detect minute variations and field strength as well as identifying any new areas where the poles are reversing.
“I think it's amazing that we can take magnetic measurements by the satellites flying at a few hundred kilometers, and say something about the deepness into the earth how the molten iron moves at a depth of about 3,000 kilometers. Is that amazing?”
Scientists hope these satellites will help them predict when the magnetic poles are about to switch. They might even save lives.
“I think that in the next decade or two, we can develop a science to forecast where the Earth's magnetic field is headed, and use that then as a planning tool; use that as a planning tool for people who fly satellites; as a planning tool for people who fly manned spaceflight and develop the technologies necessary to deal with, but say, an impending reversal.”
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| 原文地址：http://www.tingroom.com/lesson/zrbaike/2011/259956.html |