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Unit 4 Astronomy:the science of the stars 3  

2010-01-06 12:51:53|  分类: 高一英语必修3 |  标签: |举报 |字号 订阅

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Unit 4 Astronomy:the science of the stars

 

课件地址:

http://swfa.ekunet.cn/kj001/001_7349_32503497861_36442.swf

 

Added material:

  什么是黑洞?      

       就是在宇宙中有那么一些点,这些点的体积趋向于零而密度变得无穷大,由于具有强大的吸引力,物体只要进入离这个点一定距离的范围内,就会被这个强大的引力吸收掉,连光线也不例外。因此任何进入这个范围的物体都无法再逃出来,就是说,没有任何信号能够从这个范围内传出,因此这个范围的界限被称作视界,里面的情形人类无法看到。所以科学家给它起了个名字叫黑洞,英文就是black hole。 一颗燃烧尽了的恒星由于自身的重力而不断坍缩,最后就会形成黑洞。 

历时30年霍金改观点 称黑洞能“吸”能“吐”

从事宇宙黑洞研究近三十年的世界天体物理学泰斗斯蒂芬·霍金在前不久承认“黑洞悖论”有误之后,21号,他在爱尔兰都柏林举行的一个学术研讨会上终于就自己的新发现向外界进行了详细阐述。

黑洞是宇宙中引力极强的区域。19世纪70年代,霍金首次提出黑洞能够辐射能量的理论,但是在引入这一理论的同时,霍金也制造了物理学上的一个巨大难题,因为他认为

黑洞辐射不包含以前吸入物质的相关信息,而且随着黑洞的消失,曾经存在的黑洞的相关信息也会消失于无形。这与量子力学中认为物质信息不会完全消失的理论相矛盾。对此,过去近30年来,霍金的解释是:黑洞中的量子运动是一种特殊情况,这种说法受到了许多科学家的质疑。

如今,霍金终于改变了观点,在当天召开的学术研讨会上,霍金说,根据他的最新发现,黑洞并非只是吞噬物质。除了会在星系形成的过程中扮演重要角色外,在经过一段相当漫长的时间后,黑洞也会把一些曾被它吸入的物质信息向外界释放出来。

霍金的最新阐述被不少人称为黑洞理论的一个重要逆转。美国加州理工学院的理论物理学家约翰·普雷斯基就是其中之一。20多年前,霍金提出黑洞辐射理论时,普雷斯基就一直坚持物质信息不会完全消失,当时两人还因此打赌。所以,在当天结束演讲后,霍金将一本百科全书赠予普雷斯基,作为打赌输了的代价,而普雷斯基则获得了全场的热烈掌声。

Black holes

 (1) What is a black hole? Well, it's difficult to answer this question, since the terms we would normally use to describe a scientific phenomenon are inadequate here. Astronomers and scientists think that a black hole is a region of space (not a thing ) into which matter has fallen and from which nothing can escape---- not even light. So we can't see a black hole. A black hole experts a strong gravitational pull and yet it has no matter. It is only space ---- or so we think . how can this happen?

 (2) The theory is that some stars explode when their density increases to a particular point; they collapse and sometimes a supernova occurs. Form earth , a supernova looks like a very bright light in the sky which shines even in the daytime. Supernovae were reported by astronomers in the seventeenth and eighteenth centuries. Some people think that the Star of Bethlehem could have been a supernova. The collapse of a star may produce a White Dwarf or a neutron star--- a star , whose matter is so dense that it continually shrinks by the force of its own gravity. But if the star is very large (much bigger than our sun) this process of shrinking may be so intense that a black hole results. Imagine the earth reduced to the size of a marble, but still having the same mass and a stronger gravitational pull, and you have some idea of the force of a black hole. Any matter near the black hole is sucked in. It is impossible to say what happens inside a black hole. Scientists have called the boundary area around the hole the " event horizon." We know nothing about events which happen once objects pass this boundary. But in theory, matter must behave very differently inside the hole.

 (3) For example , if a man fell into a black hole, he would think that he reached the center of it very quickly. However an observer at the event horizon would think that the man never reached the center at all. Our space and time laws don't seem to apply to objects in the area of a black hole. Einstein's relativity theory is the only one which can explain such phenomena , so that there is no " absolute" time and space depend on the position of the observer. They are relative. We do not yet fully understand the implications of the relativity theory; but it is interesting that Einstein's theory provided a basis for the idea of black holes before astronomers started to find some evidence for their existence. It is only recently that astronomers have begun specific research into black holes. In August 1977, a satellite was launched to gather data about the 10 million black holes which are thought t be in the Milky way. And astronomers are planning a new observatory to study the individual exploding stars believed to be black holes.

 (4) The most convincing evidence of black holes comes from research into binary star systems. Binary stars, as their name suggests ,are twin stars whose position in space affects each other. In some binary systems, astronomers have shown that there is an invisible companion star, a "partner" to the one which we can see in the sky. Matter from the one we can see is being pulled towards the companion star. Could this invisible star, which exerts such a great force , be a black hole? Astronomers have evidence of a few other stars too, which might have black holes as companions.

 (5) The story of black holes is just beginning . Speculations about them are endless. There might be a massive black hole at the center on our galaxy swallowing up stars at a very rapid rate. Mankind may one day meet this fate. On the other hand, scientists have suggested that very advanced technology could one day make use of the energy of black holes for mankind. These speculations sound like science fiction. But the theory of black holes in space is accepted by many serious scientists and astronomers .they show us a world which operates in a totally different way from our own and they question our most basic experience of space and time.

 

Read the passage carefully and choose the best answer for the following questions

1) Black holes are related to ____

A.     geography B. astronomy C. physics D. economic

 2) A black hole is ____

A.     a dark star  B. a large heavenly body

C. a region of space  D. a great mass of matter

 3) what causes some stars to explode, theoretically speaking ?

A. their density B. their gravity. C. their movement D. their light

 

4) Scientists call the area around the black hole ____.

A.     a White Dwarf   B. a supernova

C. the event horizon  D. the star of Bethlehem

 5) according to Einstein's relativity theory, there is no "absolute " time and space. Is it true or false?

A. true B. false

 6) which of the following statements is not true? The story of black holes in space____

A. is accepted by many serious scientists and astronomers

B. has to some extent been proved by research into binary star system

C. is questioning our basic idea of space and time

D. Sounds like science fiction

 7) according to the passage , our earth may be swallowing by the black hole one day, is it true or false ?

A.     true B. false

 8) according to the passage , the human being one day may make use of the energy of black hole by advanced technology. Is it true or false?

A. true B. false

 

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