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托福听力必备背景知识：天文学

2015-04-21 11:03:17来源：网络

　　托福听力考试中常常会遇到关于天文学的背景资料。了解一些相关知识有助于更好的理解和做题。新东方在线为大家带来托福听力必备背景知识：天文学，希望对大家托福备考有所帮助，更多精彩尽请关注新东方在线托福网!

　　理科段子：天文学

　　In ancient times, many people believed the earth was a flat disc. Well over 2,000 years ago; the ancient Greek philosophers were able to put forward two good arguments proving that it was not. Direct observations of heavenly bodies were the basis of both these arguments. First, the Greeks knew that during eclipses of the moon the earth was between the sun and the moon, and they saw that during these eclipses, the earth's shadow on the moon was always round, they realized that this could be true only if the earth was spherical, It the earth was a flat disc, then its shadow during eclipses would not be a prefect circle; it would be stretched out into a long ellipse. The second argument was based on what the Greeks saw during their travels. They noticed that the North Star, or Polaris, appeared lower in the sky when they traveled south, in the more northerly regions, the North Star appeared to them to be much higher in the sky. By the way, it was also from this difference in the apparent position of the North Star that the Greeks first calculated the approximate distance around the circumference of the earth, a figure recorded in ancient documents says 400.000 stadium, that's the plural of the world stadium. Today, it's not known exactly what length one stadium represents, but let's say it was about 200 meters, the length of many athletic stadiums. This would make the Greek's estimate about twice the figure accepted today, a very good estimate for those writing so long before even the first telescope was invented.

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本文关键字: 托福听力 托福听力背景知识 天文

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