a visit to the moon

课堂教学设计(3)

课题：R eading: A visit to the moon and black hole 授课时数 1

Teaching procedures

Step1. Lead in

T: We all know that the earth has great gravity, so we can’t jump too high and won’t float in the air. Who first got the idea of gravity?

Ss: Isaac Newton

T: how did he get the idea?

Ss: one day he was sitting under a tree, he saw an apple fall, then he got the idea of gravity.

T: is the moon’s gravity the same as that on the earth?

Ss: no

T: what’s it like to be on the moon? Do you have any experience of weightlessness? No? There are two boys who have just come back after traveling to the moon. Do you want to know what happened to them? Ok, now, let’s learn it together. These two boys will share their experience with us.

Step2. Reading1

1. Read the passage carefully and then write down the three ways in which gravity changed for Li Yanping.

Answers:

(1) The gravity became very strong

(2) The gravity disappeared

(3) It became very light

A. His weight is normal

B. He is weightless

C. He weighs less than on earth

2. True or false

1. The force of gravity would change three times on their journey . ( )

2. When they were on the moon, they would not feel the gravity because there was no gravity on the moon. ( )

3. it’s easier for them to walk on the moon than on the earth. ( )

Step3. Reading task2

1. Fill in the chart.

T: We all know that the gravity of the moon isn’t strong. But just imagine that the moon has great gravity, what will happen?

Ss: it will pull us.

T: Right. Maybe when we are approaching it, we will be caught in it. So let’s come to the black hole now.

Look at the passage on page 66, listen to the tape carefully, and then fill in the chart.

2. Expansion

Give students more information about the black hole to widen their views.

黑洞是一种很可怕的现象，就宇宙来讲，只要经过黑洞的物质体，包括光、任何的波，都会被黑洞所吸住而且无所遁形。连光都无法逃掉黑洞的吸引。也就是说，一个黑洞可以把整个的太阳或者整个的恒星、行星整个的吸进来。而它的存在却是漂浮不定的，为什么会有黑洞的存在呢？除了我们刚所讲的恐惧的因素形成以外，其实也因为这些黑洞的存在，造就另外一端的宇宙的存在。

黑洞很可能是宇宙风形成的漩涡，也可能是引力形成的漩涡。

与别的天体相比，黑洞是显得太特殊了。例如，黑洞有“隐身术”，人们无法直接观察到它，连科学家都只能对它内部结构提出各种猜想。那么，黑洞是怎么把自己隐藏起来的呢？答案就是——弯曲的空间。我们

都知道，光是沿直线传播的。这是一个最基本的常识。可是根据广义相对论，空间会在引力场作用下弯曲。这时候，光虽然仍然沿任意两点间的最短距离传播，但走的已经不是直线，而是曲线。形象地讲，好像光本来是要走直线的，只不过强大的引力把它拉得偏离了原来的方向。

(视频)

Step6. Homework