When you look up into the sky at night, have you ever felt that your eyes are playing tricks on (捉弄) you? It seems that the stars are moving all the time.

Actually, there is nothing wrong with your eyes. This twinkling effect is called scintillation (交光). Scintillation happens because of air movements in the earth’s atmosphere (大气). Light is “bent (弯曲的)” when it travels through different parts of the earth’s atmosphere. As the air in the earth’s atmosphere is moving all the time, the light from the stars looks as if it is moving too.

The same thing also happens to things on the ground. On a very hot and shiny day, if you look at the road, the image in the distance is not clear and things move slightly. You can also see the same effect if you drop a rock into water. The rock appears a little unclear under the moving water.

This twinkling effect causes a lot of problems for astronomers (天文学家) since they cannot observe the stars clearly. A telescope (望远镜) was sent into space so that the air movements in the atmosphere could be avoided (避免). It took a long time to build the space telescope but finally in 1990, a huge space telescope called the Hubble Space Telescope was successfully sent into space. Since then, astronomers have many important observations that have helped people understand space better.

根据短文内容，选择最佳选项。 （10分）

1.What happens to the light from the stars we see when the air in the earth’s atmosphere is moving?

A．It looks even brighter.

B．It looks as if it is bent.

C．It looks as if it is moving.

D．It looks like drops of rain.

2.Scintillation also happens on 　　　　 according to the passage.

A．rainy days                             B．shiny days

C．cloudy days                            D．windy days

3.What can you see when you drop a rock into the water?

A．The rock gets broken.

B．The rock becomes unclear.

C．The water becomes much polluted.

D．The water does not move anymore.

4.The underlined word “observe” means “　　　　”.

A．watch            B．listen             C．draw             D．explain

5.Why is scintillation a problem for astronomers?

A．The stars never stay still.

B．It makes the stars too dark to see.

C．It makes astronomers feel too hot to work.

D．Astronomers cannot observe the stars clearly.

 

In the summer of 1978 an English man named Steven was driving his tractor through a field of wheat when he discovered something strange. Some of his wheat was lying on the ground. The flattened wheat formed(形成)a circle about six meters across . Around this circle were four smaller circles of flattened wheat.
　 Three years later a farmer who lived nearby discovered almost the same circles in one of his fields. These circles were larger—nearly 15 meters across . That same year , another English farmer discovered three circles of flattened wheat on his land—one large circle between two small circles. During the following years, farmers in England found circles in their fields more and more often.
　 The circles are called “crop circles” because they usually appear in fields of wheat or corn. The wheat in the circles lies on the ground but is never broken; it keeps on growing, and the farmers can later harvest it. Farmers always discover the crop circles in the morning, so the circles probably form at night. They appear only in the months from May to September. What causes the crop circles?
　 At first, people thought that some kids were making them as a joke, or that farmers were making them to attract tourists.(In fact, in 1991, two men said they made the circles themselves, but many scientists don’t believe them.) People tried to copy them: They tried to make circles exactly like the ones the farmers had found. They couldn’t do it. They couldn’t enter a field of wheat without leaving tracks, and they couldn’t flatten the wheat without breaking it.
　 Several times people reported seeing stranger objects near the fields where crop circles later appeared. Many people believe that these crop circles are the messages sent by living things from outer space(外层空间)or the marks left by their spaceships.
　 Scientists who have studied the crop circles try to find out what causes them. In the summer of 1990 some scientists spent three weeks in the part of England where many circles have appeared. They had all the latest high-tech equipment(最新高科技设备). The equipment—worth 1.8 million dollars—got nothing. But one night, as the scientists were watching a field, crop circles formed in the field behind them, which were quite different from the others. The scientists had neither seen nor heard anything.
　 When Steven discovered the crop circles on his land in 1978, he said, “It was just like something that had landed in the field from the air and gone back up again. I don’t know what to make of these things.”
　 Crop circles have appeared in England, Japan, the United States and Russia. Experts from all over the world have studied them, and they say what Steven said: They don’t know what to make of these things.
【小题1】Which picture is probably the one formed in the field behind the scientists?

【小题2】“Flattened wheat” means ___________.
　　  

A．broken wheat

B．lying wheat

C．harvested wheat

D．growing wheat

【小题3】The passage is mainly about something ___________ .

A．that is done by living things from outer space

B．that cannot be solved but found all around the world

C．that cannot be made clear or understood

D．that is discovered and copied by the farmers

When you look up into the sky at night, have you ever felt that your eyes are playing tricks on (捉弄) you? It seems that the stars are moving all the time.
Actually, there is nothing wrong with your eyes. This twinkling effect is called scintillation (交光). Scintillation happens because of air movements in the earth’s atmosphere (大气). Light is “bent (弯曲的)” when it travels through different parts of the earth’s atmosphere. As the air in the earth’s atmosphere is moving all the time, the light from the stars looks as if it is moving too.
The same thing also happens to things on the ground. On a very hot and shiny day, if you look at the road, the image in the distance is not clear and things move slightly. You can also see the same effect if you drop a rock into water. The rock appears a little unclear under the moving water.
This twinkling effect causes a lot of problems for astronomers (天文学家) since they cannot observe the stars clearly. A telescope (望远镜) was sent into space so that the air movements in the atmosphere could be avoided (避免). It took a long time to build the space telescope but finally in 1990, a huge space telescope called the Hubble Space Telescope was successfully sent into space. Since then, astronomers have many important observations that have helped people understand space better.
根据短文内容，选择最佳选项。 （10分）
【小题1】What happens to the light from the stars we see when the air in the earth’s atmosphere is moving?

A．It looks even brighter.

B．It looks as if it is bent.

C．It looks as if it is moving.

D．It looks like drops of rain.

【小题2】Scintillation also happens on 　　　　 according to the passage.

A．rainy days	B．shiny days
C．cloudy days	D．windy days

【小题3】What can you see when you drop a rock into the water?

A．The rock gets broken.

B．The rock becomes unclear.

C．The water becomes much polluted.

D．The water does not move anymore.

【小题4】The underlined word “observe” means “　　　　”.

A．watch

B．listen

C．draw

D．explain

【小题5】Why is scintillation a problem for astronomers?

A．The stars never stay still.

B．It makes the stars too dark to see.

C．It makes astronomers feel too hot to work.

D．Astronomers cannot observe the stars clearly.

If you look at the sky one night and see something moving and shining that you have never seen before, it might be a comet (彗星).

　　A comet sometimes looks like a star. Like a planet, a comet has no light of its own. It shines from the sunlight it reflects (反射). Like the earth, a comet goes round the sun, but on a much longer path (轨道) than the earth travels.

       If a comet isn’t a star, what is it then?

　   Some scientists think that a large part of a comet is water frozen into pieces of ice and mixed with iron and rock dust and perhaps a few big pieces of rock. When sunshine melts (融化) the ice in the comet, great clouds of gas go trailing after it. These clouds, together with the dust, form a long tail.Many people perhaps have seen a comet. However no one knows how many comets there are. There may be millions of comets, but only a few come close enough for us to see.

　　An Englishman named Edmund Halley, who lived from 1656 to 1742, found out a lot about the paths that comets take through the sky. Some comets move out of our sight and never come back. Others keep coming back at regular times. A big comet that keeps coming back was named after Halley because he was the one who worked out when it would come back again. Maybe you have ever seen Halley’s Comets because the last time it came close to the sun and the earth was in the year 1986. Then people all over the world were outside at night to look at it. You will probably be able to see Halley’s Comets when it comes near the earth again.

1.A comet is like ________.

A. sun      B. moon     C. sunlight    D. the earth

2.A large part of a comet is ______.

A. water and rock

B. water frozen into pieces of ice and mixed with iron

C. ice, iron and rock dust

D. only a few big pieces of rock

3.Maybe many people _______.

A. haven’t seen any comets      B. have seen all comets

C. have seen a comet at daytime  D. have seen a comet

4.Some comets keep coming back ________.

A. at any time  B. at noon  C. at regular times  D. at daytime

5.Halley’s Comets came back _____.

A. in 1990    B. in 1980     C. in 1986      D. in 1989