资源描述
111Unit 4 Astronomy: the science of the starsTeaching goals 教学目标1 Target language目标语言a. 重点词汇和短语force, gradually, float, mass, cheer up, now that, break outb.重点句子： When we get closer to the moon, we shall feel its gravity pulling us but it will not be as strong a pull as the earths. P30Walking does need a bit of practice now that gravity has changed. P31We watched, amazed as fire broke out on the outside of the spaceship the earths gravity increased. P312 Ability goals 能力目标a Discuss the three ways in which gravity changed on the moon. and some information about black holes.b. Discuss the questions about the passage: How did gravity change on the moon? What does a black hole look like? What will happen if an object is near the black hole? Teach the Ss to read passages with feeling.3 Learning ability goals 学能目标Enable the Ss to get to know about gravity and black holes.Teaching important points教学重点Talk about gravity and black holes.Teaching difficult points教学难点a. Discuss the answers to the questionsb. Teach the Ss to read the passage with feeling, paying attention to pronunciation and intonation.Teaching methods教学方法a. Fast readingb. Dealing with comprehension questionsc. Discussion Teaching aids教具准备A projector, a computer, a recorder Teaching procedures & ways教学过程与方式Step I RevisionCheck homework T: Last class we have learned different ideas about gravity, what quality an astronaut should have and some equipment on a spacesuit. Now answer the question: What needs to be an astronaut?S: An astronaut should have good health, excellent degree, many years training, right height and weight. They also should be calm, firm, patient, mature and hard-working. They must be able to adapt to the harshness of life in space. Step II Reading (Page30)1.Ask the students to read the passage quickly and fill in the form. Then check the answer.T: In last lesson, we have learned some information about gravity. Today well know gravity in details. Read the passage and fill in the form.1 left the earth2 in space3 on the moonThe way gravity changed The gravity became very strong The gravity disappearedIt became very light.,The weight changedHe became very heavy.He had no weight and could float around like a feather.He was about one-sixth of his weight on the earth.2.Listen to the tape and imitate he tape. Then practice reading aloud the dialogue with feeling.3.Ask two or three pairs of Ss to read the passage with feeling.Step III Reading Task (Page66)This reading passage is about black holes. After the first reading, let the Ss answer some questions. Show the questions on the screen. Then, let them talk about the form on page 67 after reading the text again.T: Last time weve learnt something about black holes in Listening. Do you remember Stephen Hawkings idea about it? S: He thinks that black holes can both eat and spit objects out. T: Very good. Now well read the passage about black holes. Turn to Page66, read it quickly and try to find the answers to the questions.Questions: 1.Can a black hole be seen? How do you know its a black hole? 2.What happened to the spaceship from the beginning to the end?Check the answer with the whole class.Answers: 1.No, it cant be seen. You can see things disappear into what appears to be an empty space.2.At first the lights on the spaceship went out and the computer stopped working.Then the spaceship jumped and began to move around the edge of the outside of the hole.As the spaceship moved around the hole, it began to go faster and faster.But then the spaceship jumped again, and it moved sideways from the black hole.It began to increase its speed until it seemed to be going as fast as light.At last the spaceship slowed down and the computer started working again.T: Now talk about the form on Page 67 with your partners.(A few minutes later,)T: All right. Well talk about the answers.Ask several students to answer them one by one, and then show suggested answers.Suggested answers:Old ideas about black holesWas this what we found?New ideas about black holesBlack holes cannot be seen.Yes Objects are pulled towards it.YesObjects go round and round outside the mouth of the black hole.YesObjects as large as suns can disappear into the black hole.YesAll objects must go into the black hole when they are caught by its gravity.No They can be thrown far from the black hole by the energy in the black hole.Time slows down when youre close to a black hole.YesStep IV Extra-readingHere is a supplementary reading material on the screen, a passage about black holes. Read it carefully and then do some comprehension exercises with their partners. T: Till now, we have learned two passages about gravity and black holes. Here is a supplementary reading material on the screen. Read it carefully and prepare to do some reading comprehension exercises with your partners.Questions: 1.Whats a black hole?2.Why is it called black hole?3.What is called the singularity? 4.What is called the event horizon?What is a Black Hole?A black hole is what remains when a massive star dies. If you have read How Stars Work, then you know that a star is a huge, amazing fusion reactor. Because stars are so massive and made out of gas, there is an intense gravitational field that is always trying to collapse the star. The fusion reactions happening in the core are like a giant fusion bomb that is trying to explode the star. The balance between the gravitational forces and the explosive forces is what defines the size of the star. As the star dies, the nuclear fusion reactions stop because the fuel for these reactions gets burned up. At the same time, the stars gravity pulls material inward and compresses the core. As the core compresses, it heats up and eventually creates a supernova explosion in which the material and radiation blasts out into space. What remains is the highly compressed, and extremely massive core. HistoryThe concept of an object from which light could not escape (e.g., black hole) was originally proposed by Pierre Simon Laplace in 1795. Using Newtons Theory of Gravity, Laplace calculated that if an object were compressed into a small enough radius, then the escape velocity of that object would be faster than the speed of light.The cores gravity is so strong that even light cannot escape. This object is now a black hole and literally disappears from view. Because the cores gravity is so strong, the core sinks through the fabric of space-time, creating a hole in space-time - this is why the object is called a black hole. Photo courtesy NASAArtist concept of a black hole: The arrows show the paths of objects in and around the opening of the black hole.The core becomes the central part of the black hole called the singularity. The opening of the hole is called the event horizon. You can think of the event horizon as the mouth of the black hole. Once something passes the event horizon, it is gone for good. Once inside the event horizon, all events (points in space-time) stop, and nothing (even light) can escape. The radius of the event horizon is called the Schwarzschild radius, named after astronomer Karl Schwarzschild, whose work led to the theory of black holes.Suggested answers: 1. A black hole is what remains when a massive star dies. 2. Because the cores gravity is so strong, the core sinks through the fabric of space-time, creating a hole in space-time - this is why the object is called a black hole. 3.The core becomes the central part of the black hole called the singularity. 4.The opening of the hole is called the event horizon. Step V Homework Collect passages about gravity.Prepare for speaking111
展开阅读全文