Unit 4 Astronomy: the science of the stars
Teaching goals 教学目标 1 Target la nguage 目标语言 a. 重点词汇和 短语 force, gradually, float, mass, cheer up, now that, break out b.重点句子： When we get closer
to t he moon, we shall feel its gravity pulling us but it will not be as strong a pull as the earth’s. P30 Walking does need a bit of practice now that gravity has changed. P31 We watched, amazed as fire broke out on the outside of the spaceship the earth’s gravity increased. P31 2 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 f eeling. 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 questions b. Teach the Ss to read the passage with feeling, paying attention to pronunciation and intonation. Teaching methods 教学方法 a. Fast reading b. Dealing with comprehension questions c. 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 Revision Check homework T: Last class we have learned different ideas about gravity, what quality an astronaut should have and some equipmen t 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 we’ll know gravity in details. Read the passage and fill in the form. 1 left the earth The way changed gravity The gravity became very strong He became heavy. very 2 in space The gravity disappeared
源:学科网 ZXXK] [来
3 on the moon It became very light., He was about one-sixth of his weight on the earth..
The weight changed
He had no weight and could float around like a feather.
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: L ast time we’ve learnt something about black holes in Listening. Do you remember Step hen Hawking’s idea about it? S: He thinks that black holes can both eat and spit objects out. T: Very good. Now we’ll 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 it’s 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 can’t 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 s lowed 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. We’ll talk about the answers. Ask several students to answer them one by one, and then show suggested answers. Suggested answers:
Was this what we found?
New ideas about black holes
Old ideas about black holes
Black holes cannot be seen. Objects are pulled towards it. Objects go round and round outside the mouth of the black hole. Objects as large as suns can disappear into the black hole. All objects must go into the black hole when they are caught by its gravity. Time slows down when you’re close to a black hole. Yes Yes Yes
Yes No They can be thrown far from the black hole by the energy in the black hole.
Step IV Extra-reading
Here 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.What’s 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 st ar. As the star dies, the nuclear fusion reactions stop because the fuel for these reactions gets burned up. At the same time, the star's 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.
History The core's gravity is so strong that even light cannot escape. The concept of an object from Thi s object is now a black hole and literally disappears from which light could not escape (e.g., view. Becau se the core's gravity is so strong , the core sinks black hole) was originally proposed through the fabric of space-time, creating a hole in space-time by Pierre Simon Laplace in 1795. -- this is why the object is called a black hole. Using Newton's Theory of Gravity, The core becomes the central part of the black hole called the Laplace calculated that if an object singularity. The opening of the hole is called the event horizon. were compressed into a small You can think of the event horizon as the mouth of the black enough radius, then the escape hole. Once something passes the event horizon, it is gone for velocity of that object would be good. Once inside the event horizon, all "events" (points in faster than the speed of light. 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 core's 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 speaking
Photo courtesy NASA Artist concept of a black hole: The arrows show the paths of objects in and around the opening of the black hole.
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