1 since 引导的是原因状语从句，定语从句we would normally use to describe a scientific phenomenon 修饰先行词the terms “术语”
inadequate = not enough
2 句中 “ into which” 以及后面的 “ from which” 两个都是引导的定语从句，修饰先行词 a region of space “空间区域”。如果which 在定语从句中作介词的宾语，那么这个介词可以提到从句前，构成“介词+which”引导的定语从句。这里注意两个搭配 fall into ； escape from
3 A black hole exerts a strong gravitational pull and yet it has no matter.It is only space - or so we think.
a strong gravitational pull 一个很强的引力 = gravity
yet = but 但是
so we think.是倒装句，“我们认为如此” （ we think so ）
The theory is that some stars explode when their density increases to a particular point； they collapse and sometimes a supernova occurs.From earth， a supernova looks like a very bright light in the sky which shines even in the daytime.Supernova 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.
4 The theory…a supernova occurs.此句是复合句：that some stars explode when their density increases to a particular point 是表语从句； when their density increases to a particular point 是时间状语。
注意to a particular point 是固定搭配表示“达到某一点”
explode increase collapse occur
From earth， a supernova looks like a very bright light in the sky which shines even in the daytime.
6.Some people think that the Star of Bethlehem could have been a supernova.
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.
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.
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 .