全新版大学英语听说教程第三册 Unit 13

Unit 13

Part B

Text 1

The Big Bang!

In the 20th century there were two main theories to explain the origin of the universe, the big bang theory and the steady state theory. The former stated that the universe began in a massive explosion at a single point in space about 15 billion years ago. According to the latter, however, there was no big bang. The universe has always existed and always will exist. This theory saw a universe in which old galaxies¹ were continually disappearing, and constantly replaced by new galaxies. Both theories seemed incredible to the layman². But was there any evidence for either of them?

If the steady state theory were correct, the universe should have looked the same millions of years ago as it looks now. But astronomers³ have found that the old universe did not look the same as it does now. The steady state theory does not appear to be correct. But is the big bang theory any better?

If the universe had really begun with an explosion, there should exist in the universe the cosmic background radiation from the explosion. Researchers at Princeton University began searching for the radiation in the 1960s. At the same time, while studying radio signals coming from particular parts of the Milky⁴ Way, researchers at Bell Laboratories found their work hindered by background interference that seemed to be coming from every direction. It turned out that the interference was actually the cosmic background radiation.

If the steady state theory had been correct, this background radiation would not exist. So the big bang theory seems to be correct. But why did the universe explode into existence? We can never know the answer.

Questions:

1. What is the main idea of the passage you have just heard?

2. Who are supposed to be the audience of the passage?

3. What is the steady state theory about?

4. What is the big bang theory about?

Text2

The End of Time

The universe has been expanding ever since the big bang. The galaxies are rushing away from each other because of the powerful force of the initial explosion that set the universe in motion. But each planet, star, and galaxy⁵ has a force of gravity that tries to pull all the matter in the universe back together again. The two forces are in opposition⁶.

Scientists are trying to figure out which of these two forces is the more powerful, because the future of the universe depends on it. If the expansion force is greater, then the universe will continue to expand forever. And as it expands it will cool down. The universe will run down like a clock to the cold, dark and lifeless end that awaits it. But if the matter in the universe is dense⁷ enough, gravity might one day be able to overcome the expansion. The universe could stop expanding and actually turn into the opposite of the big bang, the big crunch⁸! That might lead to another big bang and the birth of another universe. The universe might have been swinging from big bang to big crunch to big bang and so on for all time.

The future of the universe hangs on how dense it is. So far astronomers think the matter in the universe is far from dense enough to stop it from expanding forever. But astronomers believe that there may be a lot of matter, called 'dark matter' in the universe that they have not yet found. If there is enough of this 'dark matter' it could hold the key to the future of the universe.

Questions:

1. What is happening to the universe?

2. What are the two forces in opposition in the universe?

3. What does the future of the universe depend on?

Part C

Galaxies in Collision

A European-led team of astronomers have obtained exciting new images of 13 very distant colliding galaxies, using the Hubble Space Telescope. These colliding objects are part of a massive galaxy cluster.

This galaxy cluster is eight billion light-years away, one of the most distant known groups of galaxies. Therefore, it is a key target for astronomers to study how galaxies formed when the universe was young. The cluster's light has taken so long to reach us that astronomers see it now as it was when the universe was less than half its present age.

Although hundreds of galaxies appear in this Hubble Space Telescope image, the astronomers selected 81 galaxies to study in detail, 13 of which are fragments of recent collisions or pairs of colliding galaxies. This is by far the largest number of colliding galaxies ever found in a cluster.

During the collision the stars in the galaxies do not really run into each other, but their orbits are strongly disturbed by powerful gravitational pull. As a result, the so-called parent galaxies lose their shape and smoother galaxies are formed. The whole merging⁹ process can take less than a billion years, a relatively¹⁰ short time in astronomy.

To astronomers, the finding indicates that, at least in some cases, big massive galaxies form through collisions between smaller ones.

Part D

Hubble's Closest Look at Mars

NASA is releasing several images taken by the Hubble Space Telescope, which is the closest yet look at the red planet. Altogether there are four images, which show the entire planet. Each view shows the planet as it completes one quarter of its daily rotation¹¹. In these views the north polar cap is turned toward the Earth and is clearly visible at the top of each picture. The images were taken in the middle of the Martian northern summer, when the polar cap was at its smallest size. During this season the sun shines continuously on the polar cap. Previous spacecraft observations have shown that this summertime polar cap is composed of water ice, just like Earth's polar caps.

The Hubble Telescope pictures reveal that great changes have occurred on the surface of Mars in the past 20 years. The Martian surface is ever changing. Some regions that were dark 20 years ago are now bright red; some areas that were bright red are now dark. Winds move sand and dust from region to region, often in huge dust storms. Over long timescales many of the larger bright and dark markings remain stable, but smaller details come and go as they are covered and then uncovered by sand and dust.

The Hubble pictures reveal that the surface of Mars is covered with a lot of volcanic¹² rocks. But mysteries still remain. Has there been life on Mars? Is there life on it now? How different is it from our own planet? These are a few of the questions waiting to be solved.

Questions:

1. How is the image of the north polar cap of Mars?

2. What is the summertime polar cap composed of?

3. When were the images of Mars taken?

4. Which of the following is true about the north polar cap of Mars in summertime?

5. What is the characteristic of the Martian surface according to observations over the past 20 years?

6. Why do smaller bright and dark markings change over time?

1 galaxies   

星系( galaxy的名词复数 )； 银河系； 一群（杰出或著名的人物）

参考例句：

• Quasars are the highly energetic cores of distant galaxies. 类星体是遥远星系的极为活跃的核心体。
• We still don't know how many galaxies there are in the universe. 我们还不知道宇宙中有多少个星系。

2 layman   

n.俗人，门外汉，凡人

参考例句：

• These technical terms are difficult for the layman to understand.这些专门术语是外行人难以理解的。
• He is a layman in politics.他对政治是个门外汉。

3 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

4 milky   

adj.牛奶的，多奶的；乳白色的

参考例句：

• Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
• I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。

5 galaxy   

n.星系；银河系；一群(杰出或著名的人物)

参考例句：

• The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
• The company has a galaxy of talent.该公司拥有一批优秀的人才。

6 opposition   

n.反对，敌对

参考例句：

• The party leader is facing opposition in his own backyard.该党领袖在自己的党內遇到了反对。
• The police tried to break down the prisoner's opposition.警察设法制住了那个囚犯的反抗。

7 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

8 crunch   

n.关键时刻；艰难局面；v.发出碎裂声

参考例句：

• If it comes to the crunch they'll support us.关键时刻他们是会支持我们的。
• People who crunch nuts at the movies can be very annoying.看电影时嘎吱作声地嚼干果的人会使人十分讨厌。

9 merging   

合并（分类）

参考例句：

• Many companies continued to grow by merging with or buying competing firms. 许多公司通过合并或收买竞争对手的公司而不断扩大。 来自英汉非文学 - 政府文件
• To sequence by repeated splitting and merging. 用反复分开和合并的方法进行的排序。

10 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

11 rotation   

n.旋转；循环，轮流

参考例句：

• Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
• The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。

12 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。