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托福听力练习-科学美国人60秒:范艾伦辐射带

2017-03-16 10:13:00来源：科学美国人60秒

点击查看>>科学美国人60秒音频：范艾伦辐射带

　　科学美国人60秒听力练习：范艾伦辐射带

　　科学美国人60秒英文文本

　　Back in 1958, at the dawn of the space age, physicist James Van Allen discovered that the Earth is ringed by high-energy charged particles. Held in place by the planet's magnetic field, these bands of radiation were named the inner and outer Van Allen Belts. They're of particular interest to NASA as they pose a potential danger to spacecraft.

　　Now a NASA mission also named for Van Allen has found something new about his belts. By looping through them repeatedly, the twin Van Allen Probes discovered a third band of radiation.

　　Or at least there were three. The two spacecraft uncovered the previously unknown structure in September. It consisted of fast-moving electrons, situated between the two previously known Van Allen Belts. The discovery was reported in the journal Science.

　　But the new structure is no longer. Four weeks after the probes found it, the third ring was wiped out by a strong shock wave emanating from the sun. Still, the unexpected finding shows that the Van Allen Belts are more complex and variable than had been assumed. And that seemingly well-established knowledge about space still may have the capacity to surprise.

　　中文翻译请点击下一页

本文关键字: 托福听力 科学美国人

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