down in on itself. The great weight of the star's outer layers moves in towards its center. The force of gravity keeps nearly all light from escaping and nothing inside can be seen from the outside. The star actually disappears from the universe into a point of infinite density（高密度）. That is a place where the laws of general relativity that govern space and time break down.

Hawking has devoted most of his life to studying these questions.

At the beginning, cosmologists believed the holes were like a \vacuum (真空) cleaner\

Hawking revolutionized the study of black holes when he proved, in 1976 that, under the strange rules of quantum physics（量子物理）, when black holes form they send out energy and lose mass in the process.

In thinking up this so-called \one of the biggest puzzles in physics.

These particles (粒子), he said, contained no information about what has been occurring inside the black hole, or how it formed. Under his theory, once the black hole disappears, all the information within it is lost.

Black holes (2)

(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 \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\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

\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 \ 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?

七、评价与反思(Assessment and reflection)

Task 1: Collect information about “the science of stars” learnt in this unit and make notes if

necessary.

Task 2: Reflection

教师反馈Teacher’s reflection:

1. Have all the teaching aims been reached? 2. Have all the Ss learnt a lot in the lessons? 3. What can be improved? …

教师对学生课堂活动的评价：

Class: Items: Name: Understandable Logical Creative Active Cooperative Others Score: 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 2 1

学生反馈Students’ reflection: 1) 自我评价Self-assessment

Class ________Name _________No _________Date __________

In this unit, you learnt about the science of stars. How comfortable do you feel doing each of the skills below?

1=Not comfortable 2=Need more practice 3=comfortable 4=very comfortable Skills Comfortable level

Talk about astronomy 1 2 3 4 Have the proper attitude towards science 1 2 3 4 Practice expressing problems and making suggestions 1 2 3 4 Use the new words and expressions 1 2 3 4 Write an outline 1 2 3 4 Use subjective clause 1 2 3 4

2) 自我反馈Reflection

1. How to be a scientist? ___________________