第一段：
1. What is a black hole?
文章开头首先提出问题：What is a black hole? （什么是黑洞？）
2. Well, it's difficult to answer this question, since the terms we would normally use to describe a scientific phenomenon are inadequate here.
it是形式主语，真正的主语是不定式短语to answer this question；since引导了原因状语从句，terms后面的we would … a scientific phenomenon是定语从句，关系代词which / that被省略；不定式短语to describe …充当目的状语。
3. 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.
into which matter has fallen and from which nothing can escape是两个并列的定语从句，同时修饰a region of space，第一个定语从句以into which引导，而第二个定语从句以from which引导，因为有fall into和escape from搭配。
4. So we can't see a black hole.
5. A black hole exerts a strong gravitational pull and yet it has no matter.
exert相当于produce，意思是"产生"。
6. It is only space-or so we think.
or so we think中的so意思是"这样"，指前一句的内容，有时置于主谓语之后，有时置于主谓语之前，例如：
I think so. 我想是这样。
当so表示"也"、"如此…（以致于…）"的意思时，so若置于句首，句子须倒装。例
如：
Mary can play the piano. So can I. 玛丽会弹钢琴，我也会。
So beautiful is the flower that everybody likes it. 这朵花如此地漂亮，大家
都喜欢它。
7. How can this happen?
此句中can是情态动词，表示可能性；通常，表示可能性的can用于否定句和疑问句。
第二段
1. The theory is that some stars explode when their density increases to a particular point; they collapse and sometimes a supernova occurs.
occur意思是"出现"。
2. From earth, a supernova looks like a very bright light in the sky which shines even in the daytime.
which引导的是定语从句，修饰前面的light，而不是sky。
3. Supernovae were reported by astronomers in the seventeenth and eighteenth centuries.
supernovae是supernova的复数形式，也可以是supernovas。
4. Some people think that the Star of Bethlehem could have been a supernova.
could have been也表示可能性，表示的时间是过去，因为"can或could + have + 过去分词"指对过去的推测。
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.
a star是同位语成分，后面whose引导非限制性定语从句。
6. 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.
much可修饰比较级，表示"比…得多"；so … that… 意思是"如此…以致于…"；result是result from…的省略，意为"（由…）产生"。
7. 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.
该句结构是"Imagine … gravitational pull, and you have …"，相当于"If you imagine … gravitational pull, you have …"；所以，当有"Do…, and + 主语 + 动词 …"结构时，可把它改写为："If you do …, 主语 + 动词 …"；have some idea of意思是"对…有所了解"。
8. Any matter near the black hole is sucked in.
suck in意思是"吸进"。
9. It is impossible to say what happens inside a black hole.
It是形式主语，真正的主语是to say what … hole，在不定式中含有宾语从句what …。
10. Scientists have called the boundary area around the hole the "event horizon."
动词call后面接复合宾语结构，the "event horizon" 宾语补足语成分。
11. We know nothing about events which happen once objects pass this boundary.
which happen是定语从句，修饰events；once意思是"一旦"，引导时间状语从句。
12. But in theory, matter must behave very differently inside the hole.
must在此句中意思是"一定"，表示推测。
第三段
1. For example, if a man fell into a black hole, he would think that he reached the center of it very quickly.
该句结构是"if 主语 + did + …, 主语 + would do …"，这叫非真实条件句，是虚拟语气结构表示与将来事实可能相反；非真实条件句的结构有：

2. However an observer at the event horizon would think that the man never reached the center at all.
该句中would think仍然是虚拟语气，语法上称这种句型为隐含条件句；never … at all或not … at all意思是"根本不"。
3. Our space and time laws don't seem to apply to objects in the area of a black hole.
seem后面可接that从句，形容词短语或to do sth；apply to意为"适用于、适应于"， 另有：apply for（申请），apply sth to sth（把…应用于…）。
4. Einstein's relativity theory is the only one which can explain such phenomena.
phenomena（现象）是phenomenon的复数形式。
5. Einstein claimed that matter and energy are interchangeable, so that there is no "absolute" time and space.
此句中so that引导结果状语从句，意为"因此、所以"，该短语有时表示"为了、以便"，有时表示"因此、所以"。试比较：

6. There are no constants at all, and measurements of time and space depend on the position of the observer.
no … at all意思是"根本没有"；depend on意为"依靠、依赖、取决于"。另有rely on, live on, feed on, rest on, draw on等搭配。
7. They are relative.
relative反义词是absolute。
8. 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.
not yet意思是"还没有"；it是形式主语，真正主语是that从句；provide sth for sb表示"为某人提供某物"，该结构也可作provide sb with sth；类似于provide的动词还有：furnish, present, supply。
9. It is only recently that astronomers have begun specific research into black holes.
It is … that …是强调结构，强调成分是时间状语only recently；该句使用了现在完成时，因为时间状语是recently；名词research后面与介词into搭配，表示"对…的研究"。
10. 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.
to gather data …是不定式短语，充当目的状语；"be thought to + 动词原形"意思是"据认为…"。
11. And astronomers are planning a new observatory to study the individual exploding stars believed to be black holes.
to study …是不定式短语，充当目的状语；believed…是过去分词短语，充当定语，可改为定语从句which are believed to …，"be believed to + 动词原形"意思是"据信…"。
第三段：
1. The most convincing evidence of black holes comes from research into binary star systems.
evidence（证据）是不可数名词；名词research后面跟介词into搭配。
2. Binary stars, as their name suggests, are two stars whose position in space affects each other.
as their name suggests是非限制性定语从句，意思是"正如它们的名字所暗示的那样、顾名思义"，as可作关系代词，指代整个主句，引导非限制性定语从句，且该从句的位置灵活，可置于主句前面，或主句后面，或主句中间。例如：
As you know, he is very clever.He is very clever, as you know. He is, as you know, very clever.
能够指代整个主句，且引导非限制性定语从句的关系代词只有两个：which 和as，但which引导的非限制性定语从句只能置于主句之后。which译为"这"，而as译为"正如"。例如：He said nothing, which made his girl friend angry.
3. 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.
a "partner" 是an invisible companion 的同位语；the one指代the star。
4. Matter from the one which we can see is being pulled towards the companion star.
此句中的the one同上句；pull意为"吸引"。
5. Could this invisible star, which exerts such a great force, be a black hole?
which exerts … force是this invisible star的非限制性定语从句，补充说明它；could be是该句的谓语动词部分，"could / can + 动词原形"可表示可能性，是对现在状态的推测，译为"可能、也许"；另有：

6. Astronomers have evidence of a few other stars too. Which might have black holes as companions.
该句中的might也可表示可能性，可用may替换，通常用于肯定句。它的结构有：

第四段：
1. The story of black holes is just beginning.
此句的story应理解为"研究"。
2. Speculations about them are endless.
speculations about …意思是：关于…的假说。
3. There might be a massive black hole at the center of our galaxy swallowing up stars at a very rapid rate.
该句的might也表示可能性；swallow up意思是"吞没"，swallowing up …是现在分词短语，修饰前面的a massive black hole，可改为定语从句which / that is swallowing up …；名词rate或speed前面的介词用at。
4. Mankind may one day meet this fate.
5. On the other hand, scientists have suggested that very advanced technology could one day make use of the energy of black holes for mankind.
on the other hand意思是"另一方面"，试比较on (the) one hand（一方面）；此句中的suggest意思是"提出、认为"， 若表示"建议"，其宾语从句则必须使用虚拟语气，动词为：(should) do型；make use of意思是"利用"。
6. These speculations sound like science fiction.
sound like意思是"听起来象"；比较：look like（看起来象）
7. But the theory of black holes in space is accepted by many serious scientists and astronomers.
本句是被动语态。
8. 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.
show可后接双宾结构，此句us是直接宾语，a world是间接宾语；in … way表示"以…的方法、方式"；different from是固定搭配。另有：the same as, similar to
Text B Worlds within Worlds
第一段：
1. First of all let us consider the earth (that is to say, the world) as a planet revolving round the sun.
first of all意思是"首先"，试比较：above all（尤其是、特别是、更重要的是）；consider是动词原形，因为let后面的宾语补足语的不定式符号"to"必须省略；revolve around意为"绕…旋转"。
2. The earth is one of nine planets which move in orbit round the sun.
one of … 意思是"…之一"，which引导的是定语从句，修饰前面的nine planets，因此which是复数意义，后面的谓语动词用复数形式move。试比较以下两种结构：
one of + 名词（复）＋关系代词（who, which, that）＋谓语动词（复）…
the only one of + 名词（复）＋关系代词（who, which, that）＋谓语动词（单）…