有人认为圣诞星可能是一颗超新星。could have + 过去分词 表示对以前发生的行为或动作的推测。 I could have told you about it， but I don't remember it now.我可能给你说过这件事，但我现在记不得了。 7.The collapse of a star…a star， whose matter is…gravity.
whose 引导非限定性定语从句，修饰star . 注意 so… that 的用法 8.Imagine the earth…a black hole.
该句的主要结构是“imagine… ， and you …”而“reduced … to marble ”和“having … pull”分别为过去分词和现在分词短语作定语，修饰the earth. mass 质量
have some idea 略知一二
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. Einstein claimed that matter and energy are interchangeable， so that there is no “absolute” time and space. There are no constants at all， and measurements of 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 to be in the Milky Way. And astronomers are planning a new observatory to study the individual exploding stars believed to be black holes. Para. 3
9.For example， …very quickly
本句是表示与现在事实相反的虚拟语气。主句谓语动词用would think ， if引导的条件状语从句谓语动词用过去时fell .
10.Our space and time laws don't seem to apply to objects in the area of a black hole. 我们的时空法则似乎不适用于黑洞区内的物体。（介词短语作定语） 11.We do not yet…relativity theory； but it is…for their existence. yet： still
此句中的it为形式主语，实际主语为that引导的主语从句 before引导时间状语从句
12.It is only recently that astronomers have begun specific research into black holes. 此句是强调句，强调状语only recently. 强调结构为 It is + 被强调部分 + that …
13.a satellite was launched to gather data about the 10 million black holes which are thought to be in the Milky Way. （about引导的介词短语作定语修饰data） which 引导定语从句修饰 holes data 的单数为datum
14.Exploding 和believed to be black holes 均为分词作定语，修饰stars
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 which 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. Para.4
15.The most…affects each other.
as 的用法，引导非限定性定语从句。修饰Binary stars “双星系” whose 引导定语从句修饰 twin stars
16.下面的几句话中的which 用作定语从句的引导词，可用于限制性定语从句，也可用于引导非限制性定语从句。that 则不可用于引导非限制性定语从句。
The story of black holes is just beginning. Speculations about them are endless. There might be a
massive black hole at the center of 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. 第三部分 Para.5
17 There might be…a very rapid rate.
swallowing up stars at a very rapid rate是现在分词短语作定语，修饰hole at the center of our galaxy 是状语 story 比较真实的故事
fiction 不太真实的故事同义词：novel 18 They show us…space and time.
此句中which 引导限定性定语从句修饰world
注意介词 in 和 from 的用法，它们各自的搭配为 in a way和 different…from 译为：他们给我们展示了一个跟我们自己的截然不同的世界。 重点句：
1.Well， it's difficult to answer this question， since the terms we would normally use to describe a scientific phenomenon are inadequate here. （第一段）
2.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. （第一段）
3.The theory is that some stars explode when their density increases to a particular point； they collapse and sometimes a supernova occurs. （第二段）
4.Some people think that the Star of Bethlehem could have been a supernova. （第二段）
5.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. （第二段）
6.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. （第二段）
7.For example， if a man fell into a black hole， he would think that he reached the center of it very quickly. （第三段）
8.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. （第三段）
9.It is only recently that astronomers have begun specific research into black holes. （第三段） 10.And astronomers are planning a new observatory to study the individual exploding stars believed to be black holes. （第三段） 11.Binary stars， as their name suggests， are twin stars whose position in space affects each other. （第四段）
12.There might be a massive black hole at the center of our galaxy swallowing up stars at a very rapid rate. （第五段）
13.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. （第五段） Text B Worlds within Worlds New Words 1.planet n.行星
2.revolve vi.旋转；绕转
3.solar a.太阳的，日光的；利用太阳光的 4.largely ad.1.大量地；2.主要地
5.glitter vi.闪闪发光，闪烁 n.闪光
6.cloudless a.无云的，晴朗的
7.unlikely a.未必可能的；靠不住的 8.astronaut n.宇航员
9.thrilling a.1.令人激动的；2.颤动的，震颤的 10.outer a.外部的
11.whereas conj.而，却；反之
12.lesser a.较小的，更少的，次要的
13.concerned a.1.有关的；2.关切的，担心的
14.microscopic a.1.显微镜的；2.微观的；3.微小的，细微的 15.whilst conj.1.当…时；2.然而；3.虽然，尽管 16.plateau （[复]plateaus或plateaux） n.高原 17.tropical a.1.热带的；2.炎热的 18.coloured a.有色的
19.religion n.宗教；宗教信仰
20.circumstance n.[pl.]情况，环境；境遇 Phrases and Expressions 1.a great many 很多 2.above all 首先，首要 3.as a rule 通常；一般说来 together with 和
First of all let us consider the earth （that is to say， the world） as a planet revolving round the sun.The earth is one of nine planets which move in orbit round the sun.These nine planets， together with the sun， make up what is called our solar systems.How this wonderful system started and what kept it working with such wonderful accuracy is largely a mystery but astronomers tell us that it is only one of millions of similar systems in space， and one of the smallest.
The stars which we see glittering in the sky on a dark and cloudless night are almost certainly the suns of other solar systems more of less like our own， but they are so far away in space that it is unlikely that we shall ever get to know very much about them.About our own solar system， however， we are learning more every day.
Before the American and Russian astronauts made their thrilling journeys into outer space it was difficult for us to realize what our earth looked like from hundreds of thousands of miles away， but the photographs which the astronauts were able to take show us the earth in space looking not very different from what the moon looks like when we look at it from the earth.The earth is， however， very different from the moon， which the American astronauts have found to be without life or vegetation， whereas our earth is very much alive in every respect.The moon， by the way， is called a satellite because it goes round our earth as well as round the sun.In our words， it goes round the sun with our earth.
The surface of our earth is covered by masses of land and larger areas of water.Let us consider the water areas first.The total water area is about three times as large as the land area.The very large separate areas of water are called “oceans” and the lesser areas are called “seas.”
In most of the oceans and seas some of the water is found to be flowing in a particular direction ―that is to say， from one part towards another part of the ocean or sea concerned.The water which is flowing in this manner is said to be moving as a “current.” There are many thousands of currents in the waters of the oceans and seas， but only certain of the stronger and better marked currents are specially named and of great importance.There currents are important because they affect the climate of the land areas close to where they flow and also because they carry large quantities of microscopic animal and vegetable life which forms a large part of the food for fishes.
The nature and characteristics of the surface of the land areas of the earth vary a great deal from area to area and from place to place.The surface of some areas consists largely of high mountains and deep valleys whilst， in other areas， most of the surface consists of plains.If one made a journey over the Continents one world find every kind of surface including mountain ranges， plains， plateaux， deserts， tropical forestlands and empty areas covered permanently by ice and snow.
When thinking and learning about the world we should not forget that our world is the home of a vary great many different people ― peoples with different coloured skins， living very different lives and having very different ideas about a great many important things such as religion， government， education and social behaviour.
The circumstances under which different people live make a great difference between the way in which they live and the way in which we live， and it ought to be our business to try to understand those different circumstances so that we can better understand people of other lands.Above all， we should avoid deciding what we think about people different from ourselves without first having learned a great deal about them and the kind of lives they have to live.It is true to say that the more we learn about other people ， the better we understand their ideas and， as a rule， the better we like those people themselves. 词汇讲解：
1.revolve v.旋转，绕转
The earth revolves round / around the sun.地球绕着太阳转。
2.solar adj.太阳的，日光的，利用太阳光的 例：the solar system 太阳系 3.whereas ： conj.而，却，反之
He must be about sixty， whereas his wife looks about thirty.他一定有60岁了，而他的妻子看起来只有30岁。
You eat a massive plate of food for lunch， whereas I have just a sandwich.你中午吃了一大盘食物，而我只吃了个三明治。
4.concerned ： 有关的，关心的，担心的
I was quite a shock for all concerned.这对所有有关人士都是一个震惊。 Her job is something concerned with English.她的工作和英语有关。 5.tropical adj.热带的，炎热的
I'd love to live somewhere with a tropical climate. 我想生活在某个属于热带气候的地方
August was almost tropical this year.今年八月十分炎热 6.circumstance n.环境，情况，境遇
We can't decide until we know all the circumstances. 我们只有在了解所有的情况后才能作出决定。 词组
1.a great many ， a good many 很多 （ 后边加可数名词） 2.above all ： 最重要的，尤其；首先
Above all ， don't forget to write.最重要的是别忘了写信。
In choosing the curtain for a room， you should consider the material from the point of view of texture， its weight， its pattern - but its colour above all .在挑选房间窗帘面料时，你应该考虑质地、重量和图案等，但最重要的是颜色。
3.as a rule ： 在多数情况下，通常，一般而言 = usually As a rule I'm home by six.我通常六点前在家。
As a rule， I only read detective novels.通常我只读侦探小说。 4.together with ： 和，连同
These new facts， together with the other evidence， prove the prisoner's innocence.这些新的事实连同其他证据证明这个犯人清白无辜。
John， together with his brother， has gone to the party.约翰连同他的兄弟一起去参加宴会了。
注意together with 作插入语时，句子的谓语动词的数取决于前面的主语。
重点句子：
1.The stars which we see glittering in the sky on a dark and cloudless night are almost certainly the suns of other solar systems more or less like our own， but they are so far away in space that it is unlikely that we shall ever get to know very much about them. which 引导定语从句
so… that…结果状语从句中it为形式主语
2.The earth is， however， very different from the moon， which the American astronauts have found to be without life or vegetation， whereas our earth is very much alive in every respect. which引导非限定性定语从句，修饰the moon vegetation 植物
whereas = while 然而
alive意为“有活力的”，在句中作表语。类似的形容词还有afraid， alone， alike， asleep， awake， aware等
in every respect 在每一个方面
3.In most of the oceans and seas some of the water is found to be flowing in a particular direction － that is to say， from one part towards another part of the ocean or sea concerned. to be flowing不定式作主语补语
concerned 是分词作定语，修饰the ocean or sea
4.There are many thousands of currents in the waters of the oceans and seas ，but only certain of the stronger and better marked currents are specially named and of great importance. Thousands/hundreds of + 名词复数 Eg.Hundreds of meters
此处waters指的是“大片的水，水域” peoples 表示人种
woods 表示森林，树木
5.The circumstances under which different people live make a great difference between the way in which they live and the way in which we live， and it ought to be our business to try to understand those different circumstances so that we can better understand people of other lands. 三个定语从句，由under which 和 两个in which 引导， 第一个：under which different people live 修饰 circumstances 第二个：in which they live 修饰 the way 第三个：in which we live 修饰 the way ought to = should 应该 business 责任，业务
it是形式主语，真正主语是to try to understand those different circumstances 目的状语从句，由so that引导 other lands 其它国家
6.Above all， we should avoid deciding what we think about people different from ourselves without first having learned a great deal about them and the kind of lives they have to live. 注意动词 avoid 后接动名词作宾语 decide 判定
what 引导宾语从句作deciding的宾语
they have to live 是省略连词的定语从句，修饰lives
7.It is true to say that the more we learn about other people， the better we understand their ideas and， as a rule， the better we like those people themselves. 注意 the more …， the better…， the better … 比较结构 Unit 2 补充语法知识
that 与 which引导定语从句的异同点 ：